169 results on '"WAVE-FUNCTIONS"'
Search Results
2. Carbon nano-clustering introducing quantum management.
- Author
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Putz, Mihai V. and Petrișor, Ioan I.
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CARBON nanofibers , *NANOTECHNOLOGY , *INFORMATION design , *CARBON , *GLOCALIZATION , *AEROSOLS - Abstract
Aiming to solve/respond the mist of the carbon-networking crisis by the present and foreseen global turbulences, either of economic, bionic, or ecologic nature, one may advance the next level approach to the cluster-to-metacluster of nano-technology mutagenesis: astralisation. Viewed as the new symmetrical/asymmetrical based openness, it surpasses the global limits of networking "contagion" by extending its boundaries in space, time and energy; actually, it extensively uses the quantum present and yet-to-come carbon-nanoscience, technology and challenges in order to design the information and substance synthesis at the distance as transmitted in nano-instances by activating specific potential of matter (industrial) and know-how (organizational): wave-functions and ordering degree combined in what it can be called as the strategic quantum management; it essentially describes how the activation of a nano-potential of a waving-system propagates(processes) and transform (taking-observable-form)through quantum-pairing of metaclusters –into the clusters (fullerenic packing), meta-clusters (via graphenic type of packing, Stone-Wales rotations included), and astralons (analogs of everted nanotubes' packing, e.g., Klein-Bottle); first strategic projection and patterning is also given in terms of a proposed chart of astralisation criteria and of associated composite index as applied on identified 8-folded ways of glocal (global-local) nano-ecolo-management. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
3. Heavy quarkonium in a holographic basis
- Author
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Vary, James [Iowa State Univ., Ames, IA (United States). Dept. of Physics and Astronomy]
- Published
- 2016
- Full Text
- View/download PDF
4. Fanpy: A python library for prototyping multideterminant methods in ab initio quantum chemistry
- Author
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Taewon D. Kim, M. Richer, Gabriela Sánchez‐Díaz, Ramón Alain Miranda‐Quintana, Toon Verstraelen, Farnaz Heidar‐Zadeh, and Paul W. Ayers
- Subjects
Chemical Physics (physics.chem-ph) ,DIATOMIC-MOLECULES ,Strongly Correlated Electrons (cond-mat.str-el) ,ab initio ,SEPARATED-PAIR APPROXIMATION ,FOS: Physical sciences ,General Chemistry ,electronic structure ,MODEL ,Condensed Matter - Strongly Correlated Electrons ,GENERALIZED ANTISYMMETRIZED PRODUCT ,Computational Mathematics ,Physics and Astronomy ,Physics - Chemical Physics ,SEMIEMPIRICAL THEORY ,FANCI ,WAVE-FUNCTIONS ,method development ,ELECTRON CORRELATION ,COUPLED-CLUSTER THEORY ,GEMINALS ,DENSITY-MATRICES ,Python - Abstract
Fanpy is a free and open-source Python library for developing and testing multideterminant wavefunctions and related ab initio methods in electronic structure theory. The main use of Fanpy is to quickly prototype new methods by making it easier to convert the mathematical formulation of a new wavefunction ansatze to a working implementation. Fanpy is designed based on our recently introduced Flexible Ansatz for N-electron Configuration Interaction (FANCI) framework, where multideterminant wavefunctions are represented by their overlaps with Slater determinants of orthonormal spin-orbitals. In the simplest case, a new wavefunction ansatz can be implemented by simply writing a function for evaluating its overlap with an arbitrary Slater determinant. Fanpy is modular in both implementation and theory: the wavefunction model, the system's Hamiltonian, and the choice of objective function are all independent modules. This modular structure makes it easy for users to mix and match different methods and for developers to quickly explore new ideas. Fanpy is written purely in Python with standard dependencies, making it accessible for various operating systems. In addition, it adheres to principles of modern software development, including comprehensive documentation, extensive testing, quality assurance, and continuous integration and delivery protocols. This article is considered to be the official release notes for the Fanpy library.
- Published
- 2022
5. Quantum influence of magnetic flux on spin-0 scalar charged particles in the presence of external field in a spinning cosmic string space-time.
- Author
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Ahmed, Faizuddin
- Subjects
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COSMIC strings , *AHARONOV-Bohm effect , *MAGNETIC fields , *PARTICLES , *ELECTROMAGNETIC interactions - Abstract
In this work, we investigate spin-0 massive charged particles in the background space-time induced by a spinning cosmic string coupled to a homogeneous external magnetic field parallel to the string including a magnetic quantum flux. We compute the energy eigenvalues and eigenfunctions and analyze a relativistic analogue of the Aharonov-Bohm effect. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
6. Monitoring the localization-delocalization transition within a one-dimensional model with nonrandom long-range interaction
- Author
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Malyshev, Andrey, Domínguez-Adame Acosta, Francisco, Malyshev, Andrey, and Domínguez-Adame Acosta, Francisco
- Abstract
© 2004 The American Physical Society. The authors thank A. Rodríguez, M. A. Martín-Delgado, and G. Sierra for discussions. This work was supported by DGI-MCyT (MAT2003-01533) and MECyD (SB2001 -0146), We consider a two-parameter one-dimensional Hamiltonian with uncorrelated diagonal disorder and nonrandom long-range intersite interaction J(mn)=J/\m-n\(mu). The model is critical at 1
- Published
- 2023
7. Quantum quenches in disordered systems: approach to thermal equilibrium without a typical relaxation time
- Author
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Khatami, Ehsan, Rigol, Marcos, Relaño Pérez, Armando, García García, Antonio M., Khatami, Ehsan, Rigol, Marcos, Relaño Pérez, Armando, and García García, Antonio M.
- Abstract
© 2012 American Physical Society. This research was supported by NSF under Grant No. OCI-0904597 (E. K. and M. R.) and by the U.S. Office of Naval Research (M. R.). A. M. G. acknowledges support from Galileo Galilei Institute, FCT (PTDC/FIS/111348/2009), Marie Curie Action (PIRG07-GA-2010-26817), and EPSRC (EP/I004637/1). A.R. acknowledges support from the Spanish Government Grants No. FIS2009-11621-C02-01 and No. FIS2009-07277., We study spectral properties and the dynamics after a quench of one-dimensional spinless fermions with short-range interactions and long-range random hopping. We show that a sufficiently fast decay of the hopping term promotes localization effects at finite temperature, which prevents thermalization even if the classical motion is chaotic. For slower decays, we find that thermalization does occur. However, within this model, the latter regime falls in an unexpected universality class, namely, observables exhibit a power-law (as opposed to an exponential) approach to their thermal expectation values., NSF, U.S. Office of Naval Research, Galileo Galilei Institute, FCT, Marie Curie Action, EPSRC, Spanish Government, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub
- Published
- 2023
8. SparseMaps-A systematic infrastructure for reduced-scaling electronic structure methods. VI. Linear-scaling explicitly correlated N-electron valence state perturbation theory with pair natural orbital
- Author
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Guo, Yang, Pavosevic, Fabijan, Sivalingam, Kantharuban, Becker, Ute, Valeev, Edward F. F., Neese, Frank, Guo, Yang, Pavosevic, Fabijan, Sivalingam, Kantharuban, Becker, Ute, Valeev, Edward F. F., and Neese, Frank
- Abstract
In this work, a linear scaling explicitly correlated N-electron valence state perturbation theory (NEVPT2-F12) is presented. By using the idea of a domain-based local pair natural orbital (DLPNO), computational scaling of the conventional NEVPT2-F12 is reduced to near-linear scaling. For low-lying excited states of organic molecules, the excitation energies predicted by DLPNO-NEVPT2-F12 are as accurate as the exact NEVPT2-F12 results. Some cluster models of rhodopsin are studied using the new algorithm. Our new method is able to study systems with more than 3300 basis functions and an active space containing 12 p-electrons and 12 p-orbitals. However, even larger calculations or active spaces would still be feasible.
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- 2023
9. Synchrotron X‐ray Electron Density Analysis of Chemical Bonding in the Graphitic Carbon Nitride Precursor Melamine
- Author
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Emilie S. Vosegaard, Maja K. Thomsen, Lennard Krause, Thomas B. E. Grønbech, Aref Mamakhel, Seiya Takahashi, Eiji Nishibori, and Bo B. Iversen
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SCATTERING FACTORS ,REFINEMENT ,EXPERIMENTAL CHARGE-DENSITY ,chemical bonding ,MODEL ENERGIES ,Organic Chemistry ,General Chemistry ,graphitic carbon nitride ,Catalysis ,CRYSTALEXPLORER ,NEUTRON-DIFFRACTION ,2,4,6-TRIAMINO-S-TRIAZINE ,melamine ,WAVE-FUNCTIONS ,CRYSTAL-STRUCTURE ,synchrotron X-ray diffraction ,ACCURATE ,electron density - Abstract
Melamine is a precursor and building block for graphitic carbon nitride (g-CN) materials, a group of layered materials showing great promise for catalytic applications. The synthetic pathway to g-CN includes a polycondensation reaction of melamine by evaporation of ammonia. Melamine molecules in the crystal organize into wave-like planes with an interlayer distance of 3.3 Å similar to that of g-CN. Here we present an extensive investigation of the experimental electron density of melamine obtained from modelling of synchrotron radiation X-ray single-crystal diffraction data measured at 25 K with special focus on the molecular geometry and intermolecular interactions. Both intra- and interlayer structures are dominated by hydrogen bonding and π-interactions. Theoretical gas-phase optimizations of the experimental molecular geometry show that bond lengths and angles for atoms in the same chemical environment (C−N bonds in the ring, amine groups) differ significantly more for the experimental geometry than for the gas-phase-optimized geometries, indicating that intermolecular interactions in the crystal affects the molecular geometry. In the experimental crystal geometry, one amine group has significantly more sp 3-like character than the others, hinting at a possible formation mechanism of g-CN. Topological analysis and energy frameworks show that the nitrogen atom in this amine group participates in weak intralayer hydrogen bonding. We hypothesize that melamine condenses to g-CN within the layers and that the unique amine group plays a key role in the condensation process.
- Published
- 2022
10. Near-exact treatment of seniority-zero ground and excited states with a Richardson-Gaudin mean-field
- Author
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Charles-Émile Fecteau, Samuel Cloutier, Jean-David Moisset, Jérémy Boulay, Patrick Bultinck, Alexandre Faribault, and Paul A. Johnson
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Chemical Physics (physics.chem-ph) ,DIATOMIC-MOLECULES ,Strongly Correlated Electrons (cond-mat.str-el) ,QUANTUM-MECHANICS ,SEPARATED PAIR APPROXIMATION ,General Physics and Astronomy ,FOS: Physical sciences ,CONFIGURATION-INTERACTION METHOD ,Condensed Matter - Strongly Correlated Electrons ,Chemistry ,ANTISYMMETRIC PRODUCTS ,Physics and Astronomy ,ORBITAL EXPANSION ,Physics - Chemical Physics ,WAVE-FUNCTIONS ,MATRIX RENORMALIZATION-GROUP ,ELECTRON ,Physical and Theoretical Chemistry ,GENERALIZED PRODUCT FUNCTIONS ,REDUCED DENSITY-MATRICES - Abstract
Eigenvectors of the reduced Bardeen-Cooper-Schrieffer (BCS) Hamiltonian, Richardson-Gaudin (RG) states, are used as a variational wavefunction ansatz for strongly correlated electronic systems. These states are geminal products whose coefficients are solutions of non-linear equations. Previous results showed an un-physical apparent avoided crossing in ground state dissociation curves for hydrogen chains. In this paper, it is shown that each seniority-zero state of the molecular Coulomb Hamiltonian corresponds directly to an RG state. However, the seniority-zero ground state does not correspond to the ground state of a reduced BCS Hamiltonian. The difficulty is in choosing the correct RG state. The systems studied showed a clear choice, and we expect that it should always be possible to reason physically which state to choose. Published under an exclusive license by AIP Publishing.
- Published
- 2022
11. Understanding Trends in Molecular Bond Angles
- Author
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Piet Th. van Duijnen, Gerrit-Jan Linker, Ria Broer, Theoretical Chemistry, Computational Chemical Physics, and MESA+ Institute
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POTENTIALS ,UT-Hybrid-D ,Electronic structure ,010402 general chemistry ,01 natural sciences ,Molecular physics ,Article ,symbols.namesake ,Polarizability ,0103 physical sciences ,WAVE-FUNCTIONS ,Physics::Atomic and Molecular Clusters ,Molecule ,Physical and Theoretical Chemistry ,Physics::Chemical Physics ,Debye ,010304 chemical physics ,Chemistry ,GEOMETRY ,Triatomic molecule ,POLARIZABILITY ,0104 chemical sciences ,MODEL ,ELECTRONIC-STRUCTURE ,Molecular geometry ,Chemical bond ,Covalent bond ,DENSITY ,ANO BASIS-SETS ,symbols ,DIHYDRIDES ,DIHALIDES - Abstract
Trends in bond angle are identified in a systematic study of more than a thousand symmetric A(2)B triatomic molecules. We show that, in series where atoms A and B are each varied within a group, the following trends hold: (1) the A-B-A bond angle decreases for more polarizable central atoms B, and (2) the A-B-A angle increases for more polarizable outer atoms A. The physical underpinning is provided by the extended Debye polarizability model for the chemical bond angle, hence our present findings also serve as validation of this simple classical model. We use experimental bond angles from the literature and, where not available, we optimize molecular geometries with quantum chemical methods, with an open mind with regards to the stability of these molecules. We consider main group elements up to and including the sixth period of the periodic table.
- Published
- 2020
12. Concerning pion parton distributions
- Author
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Z.-F. Cui, M. Ding, J. M. Morgado, K. Raya, D. Binosi, L. Chang, J. Papavassiliou, C. D. Roberts, J. Rodríguez-Quintero, and S. M. Schmidt
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Nuclear and High Energy Physics ,Nuclear Theory ,FOS: Physical sciences ,Wave-functions ,01 natural sciences ,High Energy Physics - Experiment ,Nucleon ,Nuclear Theory (nucl-th) ,High Energy Physics - Experiment (hep-ex) ,High Energy Physics - Lattice ,High Energy Physics - Phenomenology (hep-ph) ,Deep inelastic-scattering ,0103 physical sciences ,Asymptotic freedom ,ddc:530 ,22 Física ,Nuclear Experiment (nucl-ex) ,010306 general physics ,10. No inequality ,Nuclear Experiment ,Mesons ,010308 nuclear & particles physics ,High Energy Physics::Phenomenology ,High Energy Physics - Lattice (hep-lat) ,QCD ,High Energy Physics - Phenomenology ,Muon pairs ,Quark ,Model - Abstract
We are grateful for constructive comments from K.-L. Cai, O. Denisov, F. de Soto, T. Frederico, J. Friedrich, C. Mezrag, V. Mokeev, W.-D. Nowak, C. Quintans, G. Salme and J. Segovia. Work supported by: National Natural Science Foundation of China (Grant nos. 12135007, 11805097); Helmholtz-Zentrum Dresden-Rossendorf High Potential Programme; Spanish Ministry of Science and Innovation (MICINN) (Grant nos. PID2020-113334GB, PID2019-107844GBC22); Generalitat Valenciana (Grant no. Prometeo/2019/087); Junta de Andalucia (Grant nos. P18-FR-5057, UHU-1264517, UHU EPIT2021); and STRONG-2020 "The strong interaction at the frontier of knowledge: fundamental research and applications" which received funding from the European Union's Horizon 2020 research and innovation programme (grant no. 824093)., Analyses of the pion valence-quark distribution function (DF), u(pi) (x; sigma), which explicitly incorporate the behaviour of the pion wave function prescribed by quantum chromodynamics (QCD), predict u(pi) (x similar or equal to 1; sigma) similar to (1 - x)(beta(sigma)), beta(sigma greater than or similar to m(p)) > 2, where mp is the proton mass. Nevertheless, more than forty years after the first experiment to collect data suitable for extracting the x similar or equal to 1 behaviour of up, the empirical status remains uncertain because some methods used to fit existing data return a result for up that violates this constraint. Such disagreement entails one of the following conclusions: the analysis concerned is incomplete; not all data being considered are a true expression of qualities intrinsic to the pion; or QCD, as it is currently understood, is not the theory of strong interactions. New, precise data are necessary before a final conclusion is possible. In developing these positions, we exploit a single proposition, viz. there is an effective charge which defines an evolution scheme for parton DFs that is all-orders exact. This proposition has numerous corollaries, which can be used to test the character of any DF, whether fitted or calculated., National Natural Science Foundation of China (NSFC) 12135007 11805097, Spanish Government European Commission PID2020-113334GB PID2019-107844GBC22, Generalitat Valenciana European Commission, General Electric Prometeo/2019/087, Junta de Andalucia P18-FR-5057 UHU-1264517 UHU EPIT2021, STRONG-2020 "The strong interaction at the frontier of knowledge: fundamental research and applications" - European Union's Horizon 2020 research and innovation programme 824093, Helmholtz-Zentrum Dresden-Rossendorf High Potential Programme
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- 2022
13. Exact solution of the semiconfined harmonic oscillator model with a position-dependent effective mass in an external homogeneous field
- Author
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Joris Van der Jeugt and Elchin Jafarov
- Subjects
probabilities of the transitions ,OPERATORS ,Mathematics and Statistics ,harmonic oscillator ,Physics and Astronomy ,STATES ,Semiconfined harmonic oscillator ,SEMIPARABOLIC QUANTUM-WELL ,WAVE-FUNCTIONS ,General Physics and Astronomy ,UNCERTAINTY ,external homogeneous field ,Quantum mechanics - Abstract
We extend exactly solvable model of a one-dimensional non-relativistic canonical semiconfined quantum harmonic oscillator with a mass that varies with position to the case where an external homogeneous field is applied. The problem is still exactly solvable and the analytic expression of the wave functions of the stationary states is expressed by means of generalised Laguerre polynomials, too. Unlike the case without any external field, when the energy spectrum completely overlaps with the energy spectrum of the standard non-relativistic canonical quantum harmonic oscillator, the energy spectrum is now still equidistant but depends on the semiconfinement parameter a. We also compute probabilities of the transitions for the model under the external field and discuss limit cases for the energy spectrum, wave functions and probabilities of transitions, when the semiconfinement parameter a goes to infinity.
- Published
- 2022
14. The importance of kinematic twists and genuine saturation effects in dijet production at the Electron-Ion Collider
- Author
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Heikki Mäntysaari, Björn Schenke, Renaud Boussarie, Farid Salazar, Centre de Physique Théorique [Palaiseau] (CPHT), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), and Helsinki Institute of Physics
- Subjects
Nuclear Theory ,quark antiquark ,QC770-798 ,hiukkasfysiikka ,PROTON ,transverse momentum dependence ,01 natural sciences ,law.invention ,Color-glass condensate ,GLUON DISTRIBUTION-FUNCTIONS ,High Energy Physics - Phenomenology (hep-ph) ,law ,EQUATION ,Saturation (graph theory) ,Wave function ,Physics ,electron nucleon: colliding beams ,QUARK PAIR PRODUCTION ,FLUCTUATIONS ,QCD Phenomenology ,QCD phenomenology ,High Energy Physics - Phenomenology ,kinematics ,twist ,Physics::Space Physics ,Production (computer science) ,Quark ,dijet: production ,COLLISIONS ,Nuclear and High Energy Physics ,Particle physics ,[PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th] ,FOS: Physical sciences ,anisotropy ,114 Physical sciences ,dihadron: angular correlation ,deep inelastic scattering (phenomenology) ,AZIMUTHAL CORRELATIONS ,Momentum ,electron p: scattering ,Nuclear Theory (nucl-th) ,Nuclear and particle physics. Atomic energy. Radioactivity ,0103 physical sciences ,WAVE-FUNCTIONS ,010306 general physics ,Collider ,Deep Inelastic Scattering (Phenomenology) ,010308 nuclear & particles physics ,electron nucleus: scattering ,High Energy Physics::Phenomenology ,EVOLUTION ,Gluon ,[PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph] ,gluon: saturation ,color glass condensate ,High Energy Physics::Experiment ,kvanttiväridynamiikka - Abstract
We compute the differential yield for quark anti-quark dijet production in high-energy electron-proton and electron-nucleus collisions at small $x$ as a function of the relative momentum $\boldsymbol{P}_\perp$ and momentum imbalance $\boldsymbol{k}_\perp$ of the dijet system for different photon virtualities $Q^2$, and study the elliptic and quadrangular anisotropies in the relative angle between $\boldsymbol{P}_\perp$ and $\boldsymbol{k}_\perp$. We review and extend the analysis in [1], which compared the results of the Color Glass Condensate (CGC) with those obtained using the transverse momentum dependent (TMD) framework. In particular, we include in our comparison the improved TMD (ITMD) framework, which resums kinematic power corrections of the ratio $k_\perp$ over the hard scale $Q_\perp$. By comparing ITMD and CGC results we are able to isolate genuine higher saturation contributions in the ratio $Q_s/Q_\perp$ which are resummed only in the CGC. These saturation contributions are in addition to those in the Weizs\"ackerWilliams gluon TMD that appear in powers of $Q_s/k_\perp$. We provide numerical estimates of these contributions for inclusive dijet production at the future Electron-Ion Collider, and identify kinematic windows where they can become relevant in the measurement of dijet and dihadron azimuthal correlations. We argue that such measurements will allow the detailed experimental study of both kinematic power corrections and genuine gluon saturation effects., Comment: v3: typos corrected post-publication. v2: 52 pages, 13 figures, matches published version
- Published
- 2021
15. Gluon imaging using azimuthal correlations in diffractive scattering at the Electron-Ion Collider
- Author
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Kaushik Roy, Farid Salazar, Heikki Mäntysaari, Björn Schenke, and Helsinki Institute of Physics
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Particle physics ,Photon ,Nuclear Theory ,J/PSI MESONS ,Meson ,FOS: Physical sciences ,hiukkasfysiikka ,114 Physical sciences ,01 natural sciences ,ENERGY-DEPENDENCE ,Color-glass condensate ,Nuclear Theory (nucl-th) ,High Energy Physics - Phenomenology (hep-ph) ,LARGE MOMENTUM-TRANSFER ,0103 physical sciences ,WAVE-FUNCTIONS ,Vector meson ,Nuclear Experiment ,010306 general physics ,VIRTUAL COMPTON-SCATTERING ,Physics ,010308 nuclear & particles physics ,Scattering ,COLOR GLASS CONDENSATE ,EVOLUTION ,3. Good health ,Gluon ,High Energy Physics - Phenomenology ,PARTON DISTRIBUTIONS ,PHOTOPRODUCTION ,Production (computer science) ,Color charge ,VECTOR-MESON PRODUCTION - Abstract
We study coherent diffractive photon and vector meson production in electron-proton and electron-nucleus collisions within the Color Glass Condensate effective field theory. We show that electron-photon and electron-vector meson azimuthal angle correlations are sensitive to non-trivial spatial correlations in the gluon distribution of the target, and perform explicit calculations using spatially dependent McLerran-Venugopalan initial color charge configurations coupled to the numerical solution of small $x$ JIMWLK evolution equations. We compute the cross-section differentially in $Q^2$ and $|t|$ and find sizeable anisotropies in the electron-photon and electron-$\mathrm{J}/��$ azimuthal correlations ($v_{1,2} \approx 2 - 10 \%$) in electron-proton collisions for the kinematics of the future Electron-Ion Collider. In electron-gold collisions these modulations are found to be significantly smaller ($v_{1,2}, 32 figures, 18 figures
- Published
- 2021
16. Low‐Barrier Hydrogen Bonds in Negative Thermal Expansion Material H 3 [Co(CN) 6 ]
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Kasper Tolborg, Bo B. Iversen, Jacob Overgaard, Aref Mamakhel, Mattia Sist, and Mads R. V. Jørgensen
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OUTLIER ,Hydrogen ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Catalysis ,ATOMS ,neutron diffraction ,X-RAY-DIFFRACTION ,Negative thermal expansion ,WAVE-FUNCTIONS ,SCATTERING ,Physics::Atomic Physics ,electron density ,Quantitative Biology::Biomolecules ,010405 organic chemistry ,Hydrogen bond ,Ligand ,Chemistry ,chemical bonding ,Organic Chemistry ,CHARGE-DENSITY ,General Chemistry ,Hydrogen atom ,X-ray diffraction ,0104 chemical sciences ,Crystallography ,Chemical bond ,MODEL-COMPOUND ,Covalent bond ,hydrogen bonds ,X-ray crystallography ,NEUTRON ,CATALYTIC TRIAD - Abstract
The covalent nature of the low-barrier N−H−N hydrogen bonds in the negative thermal expansion material H 3[Co(CN) 6] has been established by using a combination of X-ray and neutron diffraction electron density analysis and theoretical calculations. This finding explains why negative thermal expansion can occur in a material not commonly considered to be built from rigid linkers. The pertinent hydrogen atom is located symmetrically between two nitrogen atoms in a double-well potential with hydrogen above the barrier for proton transfer, thus forming a low-barrier hydrogen bond. Hydrogen is covalently bonded to the two nitrogen atoms, which is the first experimentally confirmed covalent hydrogen bond in a network structure. Source function calculations established that the present N−H−N hydrogen bond follows the trends observed for negatively charge-assisted hydrogen bonds and low-barrier hydrogen bonds previously established for O−H−O hydrogen bonds. The bonding between the cobalt and cyanide ligands was found to be a typical donor–acceptor bond involving a high-field ligand and a transition metal in a low-spin configuration.
- Published
- 2019
17. LIGHT-STRANGE MESONS DECAYS IN THE QUARK MODEL.
- Author
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Yasser, A. M., Hassan, E. M., Fawzy, M. A., and Allosh, M. A.
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QUARK models , *MESONS , *WAVE functions , *HARMONIC oscillators , *HADRONS , *QUARKONIUMS - Published
- 2013
18. Extending the Gutzwiller approximation to intersite interactions
- Author
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Gabriel Kotliar, Nicola Lanatà, and Garry Goldstein
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Hubbard model ,Coordination number ,FOS: Physical sciences ,FUNCTIONAL-INTEGRAL APPROACH ,02 engineering and technology ,LIMIT ,01 natural sciences ,CORRELATED FERMI SYSTEMS ,FERROMAGNETISM ,Condensed Matter - Strongly Correlated Electrons ,HUBBARD-MODEL ,0103 physical sciences ,WAVE-FUNCTIONS ,Coulomb ,010306 general physics ,Wave function ,Mathematical physics ,Condensed Matter::Quantum Gases ,Physics ,Valence (chemistry) ,Strongly Correlated Electrons (cond-mat.str-el) ,PHASE-DIAGRAM ,021001 nanoscience & nanotechnology ,Uncorrelated ,Mott transition ,ELECTRONIC-STRUCTURE ,DENSITY ,Slater determinant ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology ,TRANSITION - Abstract
We develop an extension of the Gutzwiller Approximation (GA) formalism that includes the effects of Coulomb interactions of arbitrary range (including density density, exchange, pair hopping and Coulomb assisted hopping terms). This formalism reduces to the ordinary GA formalism for the multi-band Hubbard models in the presence of only local interactions. This is accomplished by combining the 1/z expansion -- where z is the coordination number and only the leading order terms contribute in the limit of infinite dimensions -- with a P^2-I expansion, where P is the Gutzwiller projector. The method is conveniently formulated in terms of a Gutzwiller Lagrange function. We apply our theory to the extended single band Hubbard model. Similarly to the usual Brinkman-Rice mechanism we find a Mott transition. A valence skipping transition is observed, where the occupation of the empty and doubly occupied states for the Gutzwiller wavefunction is enhanced with respect to the uncorrelated Slater determinant wavefunction., 13+23 pages (1+4 figures) comments welcome; v2: typos corrected, submitted to PRB; v3: Added Section II which presents our results in a simple intuitive manner
- Published
- 2020
19. Toward Highly Accurate Spin State Energetics in First-Row Transition Metal Complexes: A Combined CASPT2/CC Approach
- Author
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Jeremy N. Harvey, Milica Feldt, Quan Manh Phung, and Kristine Pierloot
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Spin states ,Physics, Atomic, Molecular & Chemical ,010402 general chemistry ,01 natural sciences ,Molecular physics ,ELECTRONIC-STRUCTURE CALCULATIONS ,Metal ,Transition metal ,0103 physical sciences ,WAVE-FUNCTIONS ,MATRIX RENORMALIZATION-GROUP ,Physical and Theoretical Chemistry ,Science & Technology ,Valence (chemistry) ,010304 chemical physics ,Chemistry, Physical ,Physics ,Energetics ,AB-INITIO CALCULATIONS ,GAUSSIAN-BASIS SETS ,HARTREE-FOCK ,0104 chemical sciences ,Computer Science Applications ,CORRELATED MOLECULAR CALCULATIONS ,Chemistry ,CHOLESKY DECOMPOSITION ,2ND-ORDER PERTURBATION-THEORY ,visual_art ,Physical Sciences ,visual_art.visual_art_medium ,BASIS-SET CONVERGENCE - Abstract
In previous work on the performance of multiconfigurational second-order perturbation theory (CASPT2) in describing spin state energetics in first-row transition metal systems [ Pierloot et al. J. Chem. Theory Comput. 2017 , 13 , 537 - 553 ], we showed that standard CASPT2 works well for valence correlation but does not describe the metal semicore (3s3p) correlation effects accurately. This failure is partially responsible for the well-known bias toward high-spin states of CASPT2. In this paper, we expand our previous work and show that this bias could be partly removed with a combined CASPT2/CC approach: using high-quality CASPT2 with extensive correlation-consistent basis sets for valence correlation and low-cost CCSD(T) calculations with minimal basis sets for the metal semicore (3s3p) correlation effects. We demonstrate that this approach is efficient by studying the spin state energetics of a series of iron complexes modeling important intermediates in oxidative catalytic processes in chemistry and biochemistry. On the basis of a comparison with bare CCSD(T) results from this and previous work, the average error of the CASPT2/CC approach is estimated at around 2 kcal mol-1 in favor of high spin states. ispartof: JOURNAL OF CHEMICAL THEORY AND COMPUTATION vol:14 issue:5 pages:2446-2455 ispartof: location:United States status: published
- Published
- 2018
20. Multiresolution Quantum Chemistry in Multiwavelet Bases: Analytic Derivatives for Hartree-Fock and Density Functional Theory
- Author
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Harrison, Robert
- Published
- 2004
- Full Text
- View/download PDF
21. Quantum effects on spin-0 massive charged particles with Coulomb-type potentials in (1+2)-dimensions Gürses space-time
- Author
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Ahmed, Faizuddin
- Published
- 2019
- Full Text
- View/download PDF
22. A rigorous nonorthogonal configuration interaction approach for the calculation of electronic couplings between diabatic states applied to singlet fission
- Author
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Meilani Wibowo, Remco W. A. Havenith, Ria Broer, Theoretical Chemistry, and Stratingh Institute of Chemistry
- Subjects
SOLAR-CELLS ,Diabatic states ,Diabatic ,010402 general chemistry ,01 natural sciences ,7. Clean energy ,Biochemistry ,Nonorthogonal configuration interaction approach ,0103 physical sciences ,Physics::Atomic and Molecular Clusters ,WAVE-FUNCTIONS ,Singlet state ,Physical and Theoretical Chemistry ,Physics::Chemical Physics ,Wave function ,GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries) ,Electronic coupling ,Coupling ,010304 chemical physics ,ORGANIC PHOTOVOLTAICS ,Chemistry ,Singlet fission ,Configuration interaction ,Chromophore ,Condensed Matter Physics ,0104 chemical sciences ,Photoexcitation ,ComputingMethodologies_DOCUMENTANDTEXTPROCESSING ,Atomic physics - Abstract
For the design of efficient singlet fission chromophores, knowledge of the factors that govern the singlet fission rate is important. This rate is approximately proportional to the electronic coupling between the lowest (diabatic) spin singlet state that is populated following photoexcitation state and a so-called (TT)-T-1 state. The latter state is characterised by two triplets, each localised on one of two neighbouring molecules, which are coupled into a singlet. Here, we show the applicability of a nonorthogonal configuration interaction approach for the calculation of this electronic coupling. The advantages of this rigorous approach are that (1) the coupling can be calculated directly, (2) it includes important correlation and orbital relaxation effects, and (3) it has a clear chemical interpretation in terms of molecular states. This approach is applied to calculate the electronic coupling for a biradicaloid molecule, viz, the bis(inner salt) of 2,5-dihydroxy-1,4-dimethyl-pyrazinium. The biradicaloid molecule is, based on the energetic criteria, a promising candidate for singlet fission. We show that the electronic coupling between the molecules is also sufficiently large for singlet fission, rendering molecules based on this chemical moiety interesting singlet fission chromophores. (C) 2017 The Author(s). Published by Elsevier B.V.
- Published
- 2017
23. Qualitative and quantitative approach towards the molecular understanding of structural, vibrational and optical features of urea ninhydrin monohydrate
- Author
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Tom Sundius, T. Uma Devi, Kadali Chaitanya, D. Sajan, V. Sasikala, and Department of Physics
- Subjects
Z-scan ,Materials science ,116 Chemical sciences ,Hyperpolarizability ,02 engineering and technology ,010402 general chemistry ,114 Physical sciences ,01 natural sciences ,Crystal ,chemistry.chemical_compound ,ELECTROPHILICITY INDEX ,NBO ,WAVE-FUNCTIONS ,ABSORPTION ,Molecule ,2ND-HARMONIC GENERATION ,CRYSTAL-STRUCTURE ,General Materials Science ,Cubic nonlinearity ,Z-scan technique ,CARBOXYLIC-ACIDS ,Vibrational spectra ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,NEUTRON-DIFFRACTION ,Crystallography ,Molecular geometry ,chemistry ,DENSITY ,Molecular vibration ,Ninhydrin ,Physical chemistry ,SINGLE-CRYSTALS ,Density functional theory ,0210 nano-technology ,2ND HARMONIC-GENERATION - Abstract
In this study, single crystals of urea ninhydrin monohydrate (UNMH) have been grown by slow evaporation method. The grown crystals were characterized by FT-IR, FT-Raman and UV-Vis-NIR spectroscopies. The Kurtz and Perry powder method was employed to confirm the near-zero SHG efficiency of the as-grown centrosymmetric UNMH crystal. The third order nonlinearity of the crystal has been studied by the open aperture Z-scan method. The nonlinear absorption coefficient is calculated and the potentiality of UNMH in optical limiting applications is identified. The molecular geometry and the origin of optical non-linearity at the molecular level have been investigated by the density functional theory. The normal coordinate analysis was carried out to assign the molecular vibrational modes. Vibrational spectral studies confirms the presence of weak O-H ... O and moderate O-H ... O type hydrogen bonds in the molecule as well as O-H ... O, N-H ... O and blue-shifted C-H ... O type H-bonds in the crystal. The intramolecular charge transfer interactions and the electronic absorption mechanisms have been discussed. The static and the dynamic values of hyperpolarizabilities for UNMH were estimated theoretically by DFT methods. (C) 2017 Elsevier B.V. All rights reserved.
- Published
- 2017
24. Vibrationally resolved emission spectra of luminescent conjugated oligothiophenes from anharmonic calculations
- Author
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D. Madsen, Ove Christiansen, Patrick Norman, and Carolin König
- Subjects
Models, Molecular ,Materials science ,Molecular Conformation ,General Physics and Astronomy ,TRANSITIONS ,FRANCK-CONDON FACTORS ,02 engineering and technology ,Thiophenes ,010402 general chemistry ,Ring (chemistry) ,01 natural sciences ,Molecular physics ,Vibration ,MOLECULES ,PHOTOIONIZATION ,WAVE-FUNCTIONS ,ABSORPTION ,Emission spectrum ,Physical and Theoretical Chemistry ,Harmonic oscillator ,Fluorescent Dyes ,SPECTROSCOPY ,Anharmonicity ,Configuration interaction ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Spectrometry, Fluorescence ,STATES ,MULTIMODE ,Molecular vibration ,Quantum Theory ,Thermodynamics ,0210 nano-technology ,Luminescence ,SELF-CONSISTENT-FIELD - Abstract
We report on accurate and efficient calculations of vibrationally resolved emission spectra for oligothiophenes from anharmonic vibrational configuration interaction wave-function calculations in reduced vibrational spaces. These reduced spaces are chosen based on the independent mode displaced harmonic oscillator model. Good agreement with experiment is obtained for all-trans oligothiophenes with two to five rings also when employing only a few active modes. Vibrational modes incorporating inter-ring carbon-carbon stretches and a ring breathing mode are found to be the main players in the vibrational progression for the emission from the first excited electronic state for all investigated oligothiophene derivatives. The presented framework is here illustrated for oligothiophenes, but we have made no underlying system-dependent assumptions and believe it to become a valuable tool for the rational design of fluorescence biomarkers.
- Published
- 2019
25. Journal of Chemical Theory And Computation
- Author
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Ruth S. T. Franklin, Seonghoon Choi, W. A. Vigor, Will Handley, Jiří Etrych, W. M. C. Foulkes, Verena Neufeld, Nick S. Blunt, Thomas W. Rogers, Maria-Andreea Filip, Fionn D. Malone, James J. Shepherd, Joseph Weston, Charles J. C. Scott, James S. Spencer, Roberto Di Remigio, Alex J. W. Thom, RuQing Xu, Chemistry, Filip, Maria-Andreea [0000-0002-9551-0235], Foulkes, WMC [0000-0001-8359-1122], Malone, Fionn D [0000-0001-9239-0162], Neufeld, Verena A [0000-0002-4204-746X], Di Remigio, Roberto [0000-0002-5452-9239], Scott, Charles JC [0000-0001-9277-8327], Thom, Alex JW [0000-0002-2417-7869], Apollo - University of Cambridge Repository, Engineering & Physical Science Research Council (EPSRC), EPSRC, CSCS Swiss National Supercomputing Centre, and Engineering and Physical Sciences Research Council
- Subjects
Density matrix ,ENERGIES ,Quantum Monte Carlo ,Monte Carlo method ,FOS: Physical sciences ,Electronic structure ,Physics, Atomic, Molecular & Chemical ,0601 Biochemistry and Cell Biology ,01 natural sciences ,Full configuration interaction ,FERROMAGNETISM ,CONFIGURATION-INTERACTION ,LOCAL TREATMENT ,0103 physical sciences ,WAVE-FUNCTIONS ,0307 Theoretical and Computational Chemistry ,ALGORITHM ,Statistical physics ,Physical and Theoretical Chemistry ,Wave function ,Science & Technology ,Chemical Physics ,010304 chemical physics ,Chemistry, Physical ,Physics ,ELECTRON CORRELATIONS ,0803 Computer Software ,Computational Physics (physics.comp-ph) ,Computer Science Applications ,Chemistry ,Coupled cluster ,GAS ,physics.comp-ph ,Physical Sciences ,Diffusion Monte Carlo ,Physics - Computational Physics - Abstract
Building on the success of Quantum Monte Carlo techniques such as diffusion Monte Carlo, alternative stochastic approaches to solve electronic structure problems have emerged over the past decade. The full configuration interaction quantum Monte Carlo (FCIQMC) method allows one to systematically approach the exact solution of such problems, for cases where very high accuracy is desired. The introduction of FCIQMC has subsequently led to the development of coupled cluster Monte Carlo (CCMC) and density matrix quantum Monte Carlo (DMQMC), allowing stochastic sampling of the coupled cluster wave function and the exact thermal density matrix, respectively. In this Article, we describe the HANDE-QMC code, an open source implementation of FCIQMC, CCMC and DMQMC, including initiator and semistochastic adaptations. We describe our code and demonstrate its use on three example systems; a molecule (nitric oxide), a model solid (the uniform electron gas), and a real solid (diamond). An illustrative tutorial is also included. Public domain – authored by a U.S. government employee
- Published
- 2019
26. A dynamical approach to non-adiabatic electron transfers at the bio-inorganic interface
- Author
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Laura Zanetti-Polzi and Stefano Corni
- Subjects
Coupling ,010304 chemical physics ,Chemistry ,Monte Carlo method ,General Physics and Astronomy ,Electron ,Molecular Dynamics Simulation ,REORGANIZATION FREE-ENERGIES ,REDOX POTENTIAL SHIFT ,CYTOCHROME-C ,OXIDATION-REDUCTION ,BIOLOGICAL MOLECULES ,TUNNELING PATHWAY ,COMPLEX-SYSTEMS ,METAL-SURFACES ,WAVE-FUNCTIONS ,PROTEIN ,010402 general chemistry ,Biochemistry ,01 natural sciences ,0104 chemical sciences ,Electron transfer ,Molecular dynamics ,Inorganic Chemicals ,Chemical physics ,0103 physical sciences ,Electrodes ,Thermodynamics ,Physical and Theoretical Chemistry ,Atomic physics ,Adiabatic process ,Reduction (mathematics) ,Quantum - Abstract
A methodology is proposed to investigate electron transfer reactions between redox-active biomolecular systems (e.g. a protein) and inorganic surfaces. The whole system is modelled at the atomistic level using classical molecular dynamics - making an extensive sampling of the system's configurations possible - and the energies associated with the redox-active complex reduction are calculated using a hybrid quantum/classical approach along the molecular dynamics trajectory. The non-adiabaticity is introduced a posteriori using a Monte Carlo approach based on the Landau-Zener theory extended to treat a metal surface. This approach thus allows us to investigate the role of the energy fluctuations, determined by the dynamical evolution of the system, as well as the role of non-adiabaticity in affecting the kinetic rate of the electron transfer reaction. Most notably, it allows us to investigate the two contributions separately, hence achieving a detailed picture of the mechanisms that determine the rate. The analysis of the system configurations also allows us to relate the estimated electronic coupling to the structural and dynamic properties of the system. As a test case, the methodology is here applied to study the electron transfer reaction between cytochrome c and a gold surface. The results obtained explain the different electron transfer rates experimentally measured for two different concentrations of proteins on the electrode surface.
- Published
- 2016
27. Libraries of Extremely Localized Molecular Orbitals. 3. Construction and Preliminary Assessment of the New Databanks
- Author
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Benjamin Meyer, Alessandro Genoni, Laboratoire de Physique et Chimie Théoriques (LPCT), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), and ANR-17-CE29-0005,QuMacroRef,De nouvelles stratégies efficaces basées sur la mécanique quantique pour l'affinement de structures cristallographiques de macromolécules à haute résolution(2017)
- Subjects
electronic-structure calculations ,theoretical data-bank ,Context (language use) ,Localized molecular orbitals ,010402 general chemistry ,01 natural sciences ,Quantum chemistry ,ab-initio treatment ,Atomic orbital ,0103 physical sciences ,Linear scale ,[CHIM.CRIS]Chemical Sciences/Cristallography ,Molecule ,tailoring approach ,Statistical physics ,Physical and Theoretical Chemistry ,Wave function ,kernel energy method ,010304 chemical physics ,x-ray-diffraction ,Chemistry ,wave-functions ,charge-density refinement ,0104 chemical sciences ,[CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry ,atom scattering factors ,electrostatic potentials ,Density functional theory - Abstract
International audience; The fast and reliable determination of wave functions and electron densities of macromolecules has been one of the goals of theoretical chemistry for a long time, and in this context, several linear scaling techniques have been successfully devised over the years. Different approaches have been adopted to tackle this problem, and one of them exploits the fact that, according to the traditional chemical perception, molecules can be seen as constituted of recurring units (e.g., functional groups) with well-defined chemical features. This has led to the development of methods in which the global wave functions or electron densities of macromolecules are obtained by simply transferring density matrices or fuzzy electron densities associated with molecular fragments. In this context, we propose an alternative strategy that aims at quickly reconstructing wave functions and electron densities of proteins through the transfer of extremely localized molecular orbitals (ELMOs), which are orbitals strictly localized on small molecular units and, for this reason, easily transferable from molecule to molecule. To accomplish this task we have constructed original libraries of ELMOs that cover all the possible elementary fragments of the 20 natural amino acids in all their possible protonation states and forms. Our preliminary test calculations have shown that, compared to more traditional methods of quantum chemistry, the transfers from the novel ELMO databanks allow to obtain wave function and electron densities of large polypeptides and proteins at a significantly reduced computational cost. Furthermore, notwithstanding expected discrepancies, the obtained electron distributions and electrostatic potentials are in very good agreement with those obtained at Hartree–Fock and density functional theory (DFT) levels. Therefore, the results encourage to use the new libraries as alternatives to the popular pseudoatom-databases of crystallography in the refinement of crystallographic structures of macromolecules. In particular, in this context, we have already envisaged the coupling of the ELMO databanks with the promising Hirshfeld atom refinement technique to extend the applicability of the latter to very large systems.
- Published
- 2018
28. Charge migration engineered by localisation: electron-nuclear dynamics in polyenes and glycine
- Author
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Morgane Vacher, Andrew J. Jenkins, Iakov Polyak, Marine E. F. Bouduban, Michael J. Bearpark, Michael A. Robb, Engineering & Physical Science Research Council (EPSRC), Imperial College London, and Uppsala Universitet [Uppsala]
- Subjects
Dephasing ,Biophysics ,Diabatic ,Electron ,ATTOSECOND PULSES ,Physics, Atomic, Molecular & Chemical ,01 natural sciences ,Molecular physics ,Atomic orbital ,Ionization ,0103 physical sciences ,Teoretisk kemi ,WAVE-FUNCTIONS ,[CHIM]Chemical Sciences ,0307 Theoretical and Computational Chemistry ,Complete active space ,Physical and Theoretical Chemistry ,Physics::Chemical Physics ,010306 general physics ,Theoretical Chemistry ,Molecular Biology ,[PHYS]Physics [physics] ,0306 Physical Chemistry (incl. Structural) ,Science & Technology ,Chemical Physics ,010304 chemical physics ,Chemistry, Physical ,Physics ,Charge (physics) ,Configuration interaction ,Condensed Matter Physics ,TIME ,Chemistry ,Ehrenfest method ,Physical Sciences ,0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics ,charge migration ,IONIZATION ,coupled electron-nuclear dynamics ,localised orbitals - Abstract
We demonstrate that charge migration can be ‘engineered’ in arbitrary molecular systems if a single localised orbital – that diabatically follows nuclear displacements – is ionised. Specifically, we describe the use of natural bonding orbitals in Complete Active Space Configuration Interaction (CASCI) calculations to form cationic states with localised charge, providing consistently well-defined initial conditions across a zero point energy vibrational ensemble of molecular geometries. In Ehrenfest dynamics simulations following localised ionisation of -electrons in model polyenes (hexatriene and decapentaene) and -electrons in glycine, oscillatory charge migration can be observed for several femtoseconds before dephasing. Including nuclear motion leads to slower dephasing compared to fixed-geometry electron-only dynamics results. For future work, we discuss the possibility of designing laser pulses that would lead to charge migration that is experimentally observable, based on the proposed diabatic orbital approach. KEYWORDS: Ehrenfest method, coupled electron-nuclear dynamics, charge migration, localised orbital
- Published
- 2018
29. Resolving the Singlet Excited State Manifold of Benzophenone by First-Principles Simulations and Ultrafast Spectroscopy
- Author
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Javier Segarra-Martí, Antonio Monari, Xavier Assfeld, Jérémie Léonard, Marco Garavelli, Ivan Rivalta, Johanna Brazard, Marco Marazzi, Elise Dumont, Stefan Haacke, Elena E. Zvereva, Laboratoire de Chimie - UMR5182 (LC), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), A.E. Arbuzov Institute of Organic and Physical Chemistry (IOPC), Kazan Scientific Centre of the Russian Academy of Sciences, Laboratoire de Physique et Chimie Théoriques (LPCT), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Dipartimento di Chimica 'G. Ciamician', Alma Mater Studiorum Università di Bologna [Bologna] (UNIBO), Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon)-Institut de Chimie du CNRS (INC), Université de Strasbourg (UNISTRA)-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), and Segarra-Marti Javier, Zvereva Elena, Marazzi Marco, Brazard Johanna, Dumont Elise, Assfeld Xavier, Haacke Stefan, Garavelli Marco, Monari Antonio, Leonard Jeremie, Rivalta Ivan
- Subjects
0307 Theoretical And Computational Chemistry ,DNA-PHOTOSENSITIZATION ,2-DIMENSIONAL ELECTRONIC SPECTROSCOPY ,Physics, Atomic, Molecular & Chemical ,010402 general chemistry ,medicine.disease_cause ,01 natural sciences ,Molecular physics ,ABSORPTION-SPECTRA ,DENSITY-FUNCTIONAL THEORY ,PHOTOEXCITED BENZOPHENONE ,chemistry.chemical_compound ,0103 physical sciences ,Ultrafast laser spectroscopy ,medicine ,Benzophenone ,PRIMARY PHOTOISOMERIZATION EVENT ,WAVE-FUNCTIONS ,Singlet state ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Spectroscopy ,ComputingMilieux_MISCELLANEOUS ,Physics ,Science & Technology ,Chemical Physics ,010304 chemical physics ,Chemistry, Physical ,Computer Science Applications1707 Computer Vision and Pattern Recognition ,0104 chemical sciences ,Computer Science Applications ,MOLECULAR-ORBITAL METHODS ,[CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry ,Chemistry ,chemistry ,Excited state ,Physical Sciences ,ANO BASIS-SETS ,Density functional theory ,Ground state ,Ultraviolet ,OPTICAL SPECTROSCOPY - Abstract
Accurate characterization of the high-lying excited state manifolds of organic molecules is of fundamental importance for the interpretation of the rich response detected in time-resolved nonlinear electronic spectroscopies. Here, we have characterized the singlet excited state manifold of benzophenone (BP), a versatile organic photoinitiator and a well-known DNA photosensitizer. Benchmarks of various multiconfigurational/multireference (RASSCF/PT2) and time-dependent density functional theory (TD-DFT) approaches allowed assignments of experimental linear absorption signals of BP in the ultraviolet (UV) region, with unprecedented characterization of ground state absorptions in the far UV. Experimental transient absorption spectra obtained by UV-vis pump-probe spectroscopy at very short time delays are shown to be directly comparable to theoretical estimates of excited state absorptions (from the low-lying nOπ∗ and π π∗ singlet states) in the Franck-Condon region. Multireference computations provided reliable interpretation of the PP spectra, with TD-DFT results yielding a fair agreement as long as electronic transitions featuring double excitations contributions are not involved. These results lay the groundwork for further computational studies and interpretation of experimental nonlinear electronic spectra of benzophenone in more complex systems, such as BP/DNA adducts.
- Published
- 2018
30. Method for making 2-electron response reduced density matrices approximately N-representable
- Author
-
Klaas Gunst, Patrick Bultinck, Paul W. Ayers, Dimitri Van Neck, Stijn De Baerdemacker, and Caitlin Lanssens
- Subjects
Normalization (statistics) ,Matrix norm ,General Physics and Astronomy ,FOS: Physical sciences ,Positive-definite matrix ,01 natural sciences ,Schrödinger equation ,RENORMALIZATION-GROUP ,ATOMS ,symbols.namesake ,MOLECULES ,CONFIGURATION-INTERACTION ,Physics - Chemical Physics ,0103 physical sciences ,WAVE-FUNCTIONS ,Applied mathematics ,NONORTHOGONAL GEMINALS ,Physical and Theoretical Chemistry ,010306 general physics ,OPTIMIZATION ,Eigenvalues and eigenvectors ,Chemical Physics (physics.chem-ph) ,Quantum Physics ,010304 chemical physics ,Geminal ,QUANTUM-CHEMISTRY ,ELECTRONS ,Chemistry ,Coupled cluster ,Physics and Astronomy ,Norm (mathematics) ,symbols ,Quantum Physics (quant-ph) ,STRONGLY CORRELATED SYSTEMS - Abstract
In methods like geminal-based approaches or coupled cluster that are solved using the projected Schr\"odinger equation, direct computation of the 2-electron reduced density matrix (2-RDM) is impractical and one falls back to a 2-RDM based on response theory. However, the 2-RDMs from response theory are not $N$-representable. That is, the response 2-RDM does not correspond to an actual physical $N$-electron wave function. We present a new algorithm for making these non-$N$-representable 2-RDMs approximately $N$-representable, i.e. it has the right symmetry and normalization and it fulfills the $P$-, $Q$- and $G$-conditions. Next to an algorithm which can be applied to any 2-RDM, we have also developed a 2-RDM optimization procedure specifically for seniority-zero 2-RDMs. We aim to find the 2-RDM with the right properties that is the closest (in the sense of the Frobenius norm) to the non-N-representable 2-RDM by minimizing the square norm of the difference between the initial 2-RDM and the targeted 2-RDM under the constraint that the trace is normalized and the 2-RDM, $Q$- and $G$-matrices are positive semidefinite, i.e. their eigenvalues are non-negative. Our method is suitable for fixing non-N-respresentable 2-RDMs which are close to being N-representable. Through the N-representability optimization algorithm we add a small correction to the initial 2-RDM such that it fulfills the most important N-representability conditions., Comment: 13 pages, 8 figures
- Published
- 2018
31. A simple algorithm for the Kohn–Sham inversion problem applicable to general target densities
- Author
-
Kati Finzel, Patrick Bultinck, and Paul W. Ayers
- Subjects
FUNCTIONALS ,Kohn-Sham potential ,Kohn–Sham equations ,Target density ,010402 general chemistry ,01 natural sciences ,Square root ,0103 physical sciences ,WAVE-FUNCTIONS ,EQUATION ,Physics::Atomic and Molecular Clusters ,Applied mathematics ,Kohn-Sham inversion procedure ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Wave function ,SIMPLE algorithm ,Eigenvalues and eigenvectors ,CONSTRUCTION ,010304 chemical physics ,Inversion (meteorology) ,EXCHANGE-CORRELATION POTENTIALS ,0104 chemical sciences ,Chemistry ,Physics and Astronomy ,Additional procedure ,GROUND-STATE ,SQUARE-ROOT ,ELECTRON-DENSITIES ,Gedanken densities ,CORRELATION ENERGIES ,Ground state - Abstract
A simple algorithm for the Kohn–Sham inversion problem is presented. The method is found to converge toward a nearby $$\nu$$ -representable Kohn–Sham density irrespective of the fact whether the initial target density has been $$\nu$$ -representable or not. For the proposed procedure, the target density can be of general nature. The algorithm can handle Hartree–Fock and post-Hartree–Fock, spin-unpolarized and polarized states equally well. Additionally, experimental densities and even general gedanken densities can be treated. The algorithm is easy to implement and does not require an additional procedure to adjust eigenvalues.
- Published
- 2018
32. A theoretical and experimental benchmark study of core-excited states in nitrogen
- Author
-
Lan Cheng, Sonia Coriani, Saikat Nandi, Henrik Koch, Marcus Gühr, Rolf H. Myhre, Thomas J. A. Wolf, Myhre, Rolf H., Wolf, Thomas J. A., Cheng, Lan, Nandi, Saikat, Coriani, Sonia, Gühr, Marku, and Koch, Henrik
- Subjects
SHELL MOLECULES ,General Physics and Astronomy ,Electronic structure ,POLARIZATION PROPAGATOR ,010402 general chemistry ,01 natural sciences ,Spectral line ,FINE-STRUCTURE NEXAFS ,Physics and Astronomy (all) ,DIAGRAMMATIC CONSTRUCTION SCHEME ,0103 physical sciences ,WAVE-FUNCTIONS ,SPECTRA ,ddc:530 ,Physical and Theoretical Chemistry ,CLUSTER RESPONSE FUNCTIONS ,Settore CHIM/02 - Chimica Fisica ,BASIS-SETS ,Physics ,SPECTROSCOPY ,010304 chemical physics ,Extended X-ray absorption fine structure ,Institut für Physik und Astronomie ,XANES ,0104 chemical sciences ,Computational physics ,Coupled cluster ,Excited state ,X-RAY-ABSORPTION ,Perturbation theory (quantum mechanics) ,Excitation - Abstract
The high resolution near edge X-ray absorption fine structure spectrum of nitrogen displays the vibrational structure of the core-excited states. This makes nitrogen well suited for assessing the accuracy of different electronic structure methods for core excitations. We report high resolution experimental measurements performed at the SOLEIL synchrotron facility. These are compared with theoretical spectra calculated using coupled cluster theory and algebraic diagrammatic construction theory. The coupled cluster singles and doubles with perturbative triples model known as CC3 is shown to accurately reproduce the experimental excitation energies as well as the spacing of the vibrational transitions. The computational results are also shown to be systematically improved within the coupled cluster hierarchy, with the coupled cluster singles, doubles, triples, and quadruples method faithfully reproducing the experimental vibrational structure. This is the authors’ accepted and refereed manuscript to the article. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in Journal of Chemical Physics and may be found at https://doi.org/10.1063/1.5011148
- Published
- 2018
33. Calculations of non-adiabatic couplings within equation-of-motion coupled-cluster framework: Theory, implementation, and validation against multi-reference methods
- Author
-
Spiridoula Matsika, Anna I. Krylov, Shirin Faraji, and Theoretical Chemistry
- Subjects
General Physics and Astronomy ,ELECTRONICALLY EXCITED-STATES ,010402 general chemistry ,01 natural sciences ,DENSITY-FUNCTIONAL THEORY ,0103 physical sciences ,Journal Article ,WAVE-FUNCTIONS ,Statistical physics ,Physical and Theoretical Chemistry ,Physics::Chemical Physics ,Wave function ,Adiabatic process ,POTENTIAL-ENERGY SURFACES ,Physics ,Coupling ,AB-INITIO ,010304 chemical physics ,Electronic correlation ,MR-CI LEVEL ,Equations of motion ,CONICAL INTERSECTIONS ,Configuration interaction ,0104 chemical sciences ,Coupled cluster ,MOLECULAR-DYNAMICS ,Density functional theory ,EXCITATION-ENERGIES ,SODIUM-DOPED CLUSTERS - Abstract
We report an implementation of non-adiabatic coupling (NAC) forces within the equation-of-motion coupled-cluster with single and double excitations (EOM-CCSD) framework via the summed-state approach. Using illustrative examples, we compare NAC forces computed with EOM-CCSD and multi-reference (MR) wave functions (for selected cases, we also consider configuration interaction singles). In addition to the magnitude of the NAC vectors, we analyze their direction, which is important for the calculations of the rate of non-adiabatic transitions. Our benchmark set comprises three doublet radical-cations (hexatriene, cyclohexadiene, and uracil), neutral uracil, and sodium-doped ammonia clusters. When the characters of the states agree among different methods, we observe good agreement between the respective NAC vectors, both in the Franck-Condon region and away. In the cases of large discrepancies between the methods, the disagreement can be attributed to the difference in the states' character, which, in some cases, is very sensitive to electron correlation, both within single-reference and multi-reference frameworks. The numeric results confirm that the accuracy of NAC vectors depends critically on the quality of the underlying wave functions. Within their domain of applicability, EOM-CC methods provide a viable alternative to MR approaches.
- Published
- 2018
34. T3NS: three-legged tree tensor network states
- Author
-
Klaas Gunst, Örs Legeza, Sebastian Wouters, Dimitri Van Neck, and Frank Verstraete
- Subjects
MODELS ,FOS: Physical sciences ,Quantum entanglement ,GROUP ALGORITHM ,01 natural sciences ,INITIO QUANTUM-CHEMISTRY ,Theoretical physics ,Condensed Matter - Strongly Correlated Electrons ,SYSTEMS ,Physics - Chemical Physics ,0103 physical sciences ,WAVE-FUNCTIONS ,Tensor ,FULL CONFIGURATION-INTERACTION ,Physical and Theoretical Chemistry ,DENSITY-MATRIX RENORMALIZATION ,010306 general physics ,Wave function ,ENTANGLEMENT ,Matrix product state ,Ansatz ,Physics ,CURVE ,Chemical Physics (physics.chem-ph) ,010304 chemical physics ,Strongly Correlated Electrons (cond-mat.str-el) ,Density matrix renormalization group ,Computer Science Applications ,Tree (data structure) ,Physics and Astronomy ,Homogeneous space - Abstract
We present a new variational tree tensor network state (TTNS) ansatz, the three-legged tree tensor network state (T3NS). Physical tensors are interspersed with branching tensors. Physical tensors have one physical index and at most two virtual indices, as in the matrix product state (MPS) ansatz of the density matrix renormalization group (DMRG). Branching tensors have no physical index, but up to three virtual indices. In this way, advantages of DMRG, in particular a low computational cost and a simple implementation of symmetries, are combined with advantages of TTNS, namely incorporating more entanglement. Our code is capable of simulating quantum chemical Hamiltonians, and we present several proof-of-principle calculations on LiF, N$_2$ and the bis($\mu$-oxo) and $\mu - \eta^2 : \eta^2$ peroxo isomers of $[\mathrm{Cu}_2\mathrm{O}_2]^{2+}$., Comment: 14 pages, 8 figures
- Published
- 2018
35. Hydrogen dynamics in solid formic acid: insights from simulations with quantum colored-noise thermostats
- Author
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M Krzystyniak, Petr Slavíček, Felix Fernandez-Alonso, Kacper Drużbicki, Giovanni Romanelli, Daniel Hollas, and Venkat Kapil
- Subjects
History ,Hydrogen ,Formic acid ,force-field ,chemistry.chemical_element ,02 engineering and technology ,01 natural sciences ,Force field (chemistry) ,scf ci ,polymorphism ,Education ,law.invention ,chemistry.chemical_compound ,law ,0103 physical sciences ,accurate ,010306 general physics ,Wave function ,Quantum ,Physics ,Settore FIS/03 ,self-consistent-field ,wave-functions ,energies ,021001 nanoscience & nanotechnology ,Thermostat ,Computer Science Applications ,nuclear-dynamics ,chemistry ,Polymorphism (materials science) ,Colors of noise ,Chemical physics ,vibrational properties ,systems ,0210 nano-technology - Abstract
With an increase of computational capabilities, ab initio molecular dynamics becomes the natural choice for exploring the nuclear dynamics of solids. As based on classical mechanics, the validity of this approach is, in-principle, limited to the high-T regime, whilst low-temperature simulations require inclusion of quantum effects. The methods commonly used to account for nuclear quantum effects are based on the path-integral formalism, which become, however, particularly time consuming when high accuracy methods are used for calculating forces. Recently, new efficient alternative approaches to account for quantum nature of nuclei have been proposed, using so-called quantum thermostats. In this work, we examine the simulations performed with the quantum colored-noise thermostat introduced by Ceriotti [Phys. Rev. Lett., 103: 030603, 2009]. We present the tests of portable implementation of the quantum thermostat in the ABIN program, which has been extended to periodic systems through the interface to CASTEP, a leading spectroscopy-oriented plane-wave density functional theory code. The range of applicability of quantum-thermostatted molecular dynamics simulations for the interpretation of neutron scattering data was examined and compared to classical molecular dynamics and lattice-dynamics simulations, using solid formic acid case as a test bed. We find that the approach is particularly useful for the modeling of low-temperature inelastic neutron scattering spectra as well as provides some theoretical estimate for the low-limit of the mean kinetic energy. While finding the quantum-thermostat to seriously affect the dynamic properties of the title system, we illustrate to which extent the unperturbed response can be successfully recovered.
- Published
- 2018
36. Guanidine: A Highly Efficient Stabilizer in Atmospheric New-Particle Formation
- Author
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Hanna Vehkamäki, Monica Passananti, Tinja Olenius, Jonas Elm, Tuomo Ponkkonen, Nanna Myllys, Institute for Atmospheric and Earth System Research (INAR), and Department of Physics
- Subjects
AUTOXIDATION PRODUCT C6H8O7 ,ION-INDUCED NUCLEATION ,Inorganic chemistry ,DENSITY FUNCTIONALS ,Evaporation ,010402 general chemistry ,114 Physical sciences ,01 natural sciences ,chemistry.chemical_compound ,SULFURIC-ACID ,SECONDARY ORGANIC AEROSOL ,0103 physical sciences ,WAVE-FUNCTIONS ,Cluster (physics) ,Molecule ,Physical and Theoretical Chemistry ,Guanidine ,Dimethylamine ,1172 Environmental sciences ,IDENTITY APPROXIMATION ,010304 chemical physics ,Chemistry ,GAUSSIAN-BASIS SETS ,Sulfuric acid ,3. Good health ,0104 chemical sciences ,MOLECULAR-ORBITAL METHODS ,Yield (chemistry) ,Particle ,CLUSTERS - Abstract
The role of a strong organobase, guanidine, in sulfuric acid-driven new-particle formation is studied using state-of-the-art quantum chemical methods and molecular cluster formation simulations. Cluster formation mechanisms at the molecular level are resolved, and theoretical results on cluster stability are confirmed with mass spectrometer measurements. New-particle formation from guanidine and sulfuric acid molecules occurs without thermodynamic barriers under studied conditions, and clusters are growing close to a 1:1 composition of acid and base. Evaporation rates of the most stable clusters are extremely low, which can be explained by the proton transfers and symmetrical cluster structures. We compare the ability of guanidine and dimethylamine to enhance sulfuric acid-driven particle formation and show that more than 2000-fold concentration of dimethylamine is needed to yield as efficient particle formation as in the case of guanidine. At similar conditions, guanidine yields 8 orders of magnitude higher particle formation rates compared to dimethylamine. Highly basic compounds such as guanidine may explain experimentally observed particle formation events at low precursor vapor concentrations, whereas less basic and more abundant bases such as ammonia and amines are likely to explain measurements at high concentrations.
- Published
- 2018
37. Information-Theoretic Approaches to Atoms-in-Molecules: Hirshfeld Family of Partitioning Schemes
- Author
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Patrick Bultinck, Ivan Vinogradov, Paul W. Ayers, Farnaz Heidar-Zadeh, Toon Verstraelen, and Esteban Vöhringer-Martinez
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NEGATIVE ,DEGENERATE GROUND-STATES ,ELECTRONIC POPULATION ANALYSIS ,Population ,LOCAL KINETIC-ENERGY ,010402 general chemistry ,Information theory ,01 natural sciences ,Measure (mathematics) ,Interpretation (model theory) ,DENSITY-FUNCTIONAL THEORY ,Fragment (logic) ,Computational chemistry ,0103 physical sciences ,WAVE-FUNCTIONS ,MANY-PARTICLE SYSTEMS ,Statistical physics ,Physical and Theoretical Chemistry ,education ,Ansatz ,education.field_of_study ,010304 chemical physics ,Chemistry ,Atoms in molecules ,GAUSSIAN-BASIS SETS ,FUKUI FUNCTIONS ,0104 chemical sciences ,Physics and Astronomy ,Density functional theory ,QUANTUM-THEORY ,MINIMAL BASIS-SETS - Abstract
Many population analysis methods are based on the precept that molecules should be built from fragments (typically atoms) that maximally resemble the isolated fragment. The resulting molecular building blocks are intuitive (because they maximally resemble well-understood systems) and transferable (because if two molecular fragments both resemble an isolated fragment, they necessarily resemble each other). Information theory is one way to measure the deviation between molecular fragments and their isolated counterparts, and it is a way that lends itself to interpretation. For example, one can analyze the relative importance of electron transfer and polarization of the fragments. We present key features, advantages, and disadvantages of the information-theoretic approach. We also codify existing information-theoretic partitioning methods in a way, that clarifies the enormous freedom one has within the information-theoretic ansatz.
- Published
- 2017
38. Computational Approach to Evaluation of Optical Properties of Membrane Probes
- Author
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Nåbo, L. J., Holmgaard List, Nanna, Steinmann, C., Kongsted, J., Nåbo, L. J., Holmgaard List, Nanna, Steinmann, C., and Kongsted, J.
- Abstract
Computed optical properties of membrane probes are typically evaluated in the gas phase, i.e. neglecting the influence of the membrane. In this study, we examine how and to what extent a membrane influences the one- and two-photon absorption (1PA and 2PA, respectively) properties for a number of cholesterol analogs and thereby also evaluate the validity of the common gas phase approach. The membrane is modeled using the polarizable embedding scheme both with and without the effective external field extension of the polarizable embedding model. The shifts in excitation energies and 1PA oscillator strengths compared to the gas phase are relatively small, while the 2PA cross section is more affected. The electric field inside the membrane induces a larger change in the permanent electric dipole moment upon excitation of the analogs compared to the gas phase, which leads to an almost 2-fold increase in the 2PA cross section for one cholesterol analog. The relative trends observed in the membrane are the same as in the gas phase, and the use of gas phase calculations for qualitative comparison and design of cholesterol membrane probes is thus a useful and computationally efficient strategy., QC 20170607
- Published
- 2017
- Full Text
- View/download PDF
39. Quantum Monte Carlo study of silicon self-interstitial defects
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Leung, WK, Needs, RJ, Rajagopal, G, Itoh, S, and Ihara, S
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diffusion quantum Monte Carlo ,1ST-PRINCIPLES CALCULATIONS ,ENERGY ,self-interstitials ,SYSTEMS ,WAVE-FUNCTIONS ,SOLIDS ,silicon ,FERMION ,self-diffusion ,density functional theory ,DIFFUSION ,STATE - Abstract
We give a brief description of the variational and diffusion quantum Monte Carlo methods and their application to the study of self-interstitial defects in silicon. The diffusion quantum Monte Carlo calculations give formation energies for the most stable defects of about 4.9 eV, which is considerably larger than the values obtained in density functional theory methods. The quantum Monte Carlo results indicate a value for the formation+migration energy of the self-interstitial contribution to self-diffusion of about 5 eV, which is consistent with the experimental data.
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- 2017
- Full Text
- View/download PDF
40. Inner products in integrable Richardson-Gaudin models
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Pieter W. Claeys, Stijn De Baerdemacker, Dimitri Van Neck, and Quantum Condensed Matter Theory (ITFA, IoP, FNWI)
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Pure mathematics ,Integrable system ,FORM-FACTORS ,Structure (category theory) ,FOS: Physical sciences ,General Physics and Astronomy ,Boundary (topology) ,Dual representation ,01 natural sciences ,Quadratic equation ,SYSTEMS ,METALLIC GRAINS ,0103 physical sciences ,WAVE-FUNCTIONS ,ALGEBRAIC BETHE-ANSATZ ,BCS MODEL ,010306 general physics ,EQUATIONS ,Mathematical Physics ,Condensed Matter - Statistical Mechanics ,Eigenvalues and eigenvectors ,Mathematics ,Statistical Mechanics (cond-mat.stat-mech) ,Nonlinear Sciences - Exactly Solvable and Integrable Systems ,010308 nuclear & particles physics ,BOUNDARIES ,Mathematical Physics (math-ph) ,State (functional analysis) ,FRAMEWORK ,lcsh:QC1-999 ,Connection (mathematics) ,Mathematics and Statistics ,CHAIN ,Exactly Solvable and Integrable Systems (nlin.SI) ,lcsh:Physics - Abstract
We present the inner products of eigenstates in integrable Richardson-Gaudin models from two different perspectives and derive two classes of Gaudin-like determinant expressions for such inner products. The requirement that one of the states is on-shell arises naturally by demanding that a state has a dual representation. By implicitly combining these different representations, inner products can be recast as domain wall boundary partition functions. The structure of all involved matrices in terms of Cauchy matrices is made explicit and used to show how one of the classes returns the Slavnov determinant formula. This framework provides a further connection between two different approaches for integrable models, one in which everything is expressed in terms of rapidities satisfying Bethe equations, and one in which everything is expressed in terms of the eigenvalues of conserved charges, satisfying quadratic equations., 21+16 pages, minor revisions compared to the previous version
- Published
- 2017
41. Time-Dependent Linear-Response Variational Monte Carlo
- Author
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Mussard, Bastien, Coccia, Emanuele, Assaraf, Roland, Otten, Matt, Umrigar, C. J., Toulouse, Julien, Mussard, B, Coccia, E, Assaraf, R, Otten, M, Umrigar, C J, Toulouse, J., Laboratoire de chimie théorique (LCT), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences du Calcul et des Données (ISCD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Sorbonne Université (SU), Dipartimento di Scienze Fisiche e Chimiche [L'Aquila], Università degli Studi dell'Aquila (UNIVAQ), Laboratory of Atomic and Solid State Physics [Ithaca] (LASSP), Cornell University [New York], Université Pierre et Marie Curie - Paris 6 (UPMC), and Università degli Studi dell'Aquila = University of L'Aquila (UNIVAQ)
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Chemical Physics (physics.chem-ph) ,Physics::Computational Physics ,Tamm-Dancoff approximation ,GEMINAL POWER ,WAVE-FUNCTIONS ,EXCITATION ,MOLECULES ,oscillator strengths ,FOS: Physical sciences ,excitation energies ,Computational Physics (physics.comp-ph) ,beryllium ,[CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry ,[PHYS.PHYS.PHYS-COMP-PH]Physics [physics]/Physics [physics]/Computational Physics [physics.comp-ph] ,linear method ,Physics - Chemical Physics ,[PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph] ,Physics - Computational Physics - Abstract
We present the extension of variational Monte Carlo (VMC) to the calculation of electronic excitation energies and oscillator strengths using time-dependent linear-response theory. By exploiting the analogy existing between the linear method for wave-function optimisation and the generalised eigenvalue equation of linear-response theory, we formulate the equations of linear-response VMC (LR-VMC). This LR-VMC approach involves the first-and second-order derivatives of the wave function with respect to the parameters. We perform first tests of the LR-VMC method within the Tamm-Dancoff approximation using single-determinant Jastrow-Slater wave functions with different Slater basis sets on some singlet and triplet excitations of the beryllium atom. Comparison with reference experimental data and with configuration-interaction-singles (CIS) results shows that LR-VMC generally outperforms CIS for excitation energies and is thus a promising approach for calculating electronic excited-state properties of atoms and molecules., Advances in Quantum Chemistry, 2017, Novel Electronic Structure Theory: General Innovations and Strongly Correlated Systems
- Published
- 2017
42. Comparison of Hydrogen Elimination from Molecular Zinc and Magnesium Hydride Clusters
- Author
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Julia Intemann, Sjoerd Harder, Peter Sirsch, Molecular Inorganic Chemistry, and Stratingh Institute of Chemistry
- Subjects
Hydrogen ,ZN-H ,Inorganic chemistry ,chemistry.chemical_element ,BASIS-SET ,Zinc hydride ,Zinc ,magnesium ,NONNUCLEAR MAXIMA ,Catalysis ,chemistry.chemical_compound ,N-HETEROCYCLIC CARBENES ,Cluster (physics) ,WAVE-FUNCTIONS ,Hydride ,Magnesium ,Organic Chemistry ,Magnesium hydride ,zinc ,hydrides ,General Chemistry ,Crystallography ,NEUTRON-DIFFRACTION ,chemistry ,Metal carbonyl hydride ,density functional calculations ,X-RAY ,cluster compounds ,COMPLEXES ,LIGANDS ,ELECTRON-DENSITY - Abstract
In analogy to the previously reported tetranuclear magnesium hydride cluster with a bridged dianionic bis-beta-diketiminate ligand, a related zinc hydride cluster has been prepared. The crystal structures of these magnesium and zinc hydride complexes are similar: the metal atoms are situated at the corners of a tetrahedron in which the vertices are bridged either by dianionic bis-b-diketiminate ligands or hydride ions. Both structures are retained in solution and show examples of H-center dot center dot center dot H- NMR coupling (Mg: 8.5 Hz; Zn: 16.0 Hz). The zinc hydride cluster [NN-(ZnH)(2)](2) thermally decomposes at 90 degrees C and releases 1.8 equivalents of H-2. In contrast to magnesium hydride clusters, there is no apparent relationship between cluster size and thermal decomposition temperature for the zinc hydrides. DFT calculations reproduced the structure of the zinc hydride cluster reasonably well and charge density analysis showed no bond paths between the hydride ions. This contrasts with calculations on the analogous magnesium hydride cluster in which a counter-intuitive H-center dot center dot center dot H- bond path was observed. Forcing a reduced H-center dot center dot center dot H- distance in the zinc hydride cluster, however, gave rise to a H-center dot center dot center dot H- bond path. Such weak interactions could play a role in H-2 desorption. The presumed molecular product after H-2 release, a Zn(I) cluster, could not be characterized experimentally but DFT calculations predicted a cluster with two localized Zn-Zn bonds.
- Published
- 2014
43. Interaction of the Dirac oscillator with the Aharonov–Bohm potential in (1+2)-dimensional Gürses space–time backgrounds.
- Author
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Ahmed, Faizuddin
- Subjects
- *
AHARONOV-Bohm effect , *ROTATIONAL symmetry , *SPACE-time symmetries , *QUANTUM theory , *EIGENVALUES - Abstract
In this paper, we study the relativistic quantum dynamics of spin- 1 2 particles interact with electromagnetic potentials in three-dimensional space–time. We solve the Dirac oscillator including the Aharonov–Bohm potential in (1+2)-dimensional rotational symmetry Gürses metric (Gürses, 1994), and analyze the Aharonov–Bohm effect on the energy eigenvalues. • Investigation of Dirac Oscillator in 3D rotational symmetry space–time and analyze the rotational effect on the eigenvalues. • Interaction with AB potential and analyze the analogue effect to the Aharonov–Bohm effects. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
44. Decomposition Pathways of the Neutral and Protonated Formamide in Some Lower-Lying Excited States
- Author
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Nguyen Tien Trung, Minh Tho Nguyen, Huyen Thi Nguyen, Vinh Son Nguyen, Remco W. A. Havenith, and Theoretical Chemistry
- Subjects
Formamide ,Protonation ,Photochemistry ,chemistry.chemical_compound ,MOLECULES ,ELECTRON-SPECTRA ,Computational chemistry ,WAVE-FUNCTIONS ,ABSORPTION ,Molecule ,AFFINITIES ,Singlet state ,Physical and Theoretical Chemistry ,AB-INITIO ,SPECTROSCOPY ,Formamides ,Photodissociation ,Decarbonylation ,PHOTODISSOCIATION ,Homolysis ,chemistry ,Excited state ,Quantum Theory ,COMPLEXES ,Protons ,QUANTUM-CHEMICAL CALCULATIONS - Abstract
Unimolecular decompositions of neutral (NH2CHO) and protonated (NH3CHO+) formamide, an active precursor of biomolecules in prebiotic chemistry, are investigated in the ground (S-0) and first triplet (T-1) and singlet (S-1) excited states. Different decomposition channels including the homolytic bond dissociations, dehydration, decarbonylation, dehydrogenation, etc., are explored using coupled-cluster theory (CCSD(T)/CBS method) for both S-0 and T-1 states and RASPT2(18,15)/6-31 G(d,p) computations for the S-1 state. On S-1 and T-1 energy surfaces, formamide preferentially follows C-N homolytic bond cleavages forming NH2 + HCO radical pairs. Formation of HCN and HNC from dehydration of neutral and protonated formamide via formimic acid and aminohydroxymethylene isomers has higher energy barriers. A strong stabilization upon triplet excitation of the two latter isomers significantly facilitates the interconversions between isomers, and thus considerably reduces the energy barriers for dehydration pathways. The most probable pathways for HCN and HNC generation are found to be dehydration of formamide in the T-1 state. Dehydration pathways from the neutral S-1 and protonated T-1 forms lead to stable complexes of HCN and HNC with water but are associated with large energy barriers. Overall, in the lower-lying excited states of either neutral or protonated formamide, dehydration is not competitive with homolytic C-N bond cleavages, which finally lead to formation of CO.
- Published
- 2013
45. Electric dipole polarizability from first principles calculations
- Author
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Giuseppina Orlandini, Mirko Miorelli, Thomas Papenbrock, Gaute Hagen, Sonia Bacca, Nir Barnea, and Gustav R. Jansen
- Subjects
Bond dipole moment ,Nuclear Theory ,Transition dipole moment ,NEUTRON RADII ,FOS: Physical sciences ,7. Clean energy ,01 natural sciences ,CROSS-SECTIONS ,Nuclear Theory (nucl-th) ,SUM-RULES ,Polarizability ,0103 physical sciences ,WAVE-FUNCTIONS ,Continuum (set theory) ,Physics::Atomic Physics ,010306 general physics ,Physics ,NUCLEI ,010308 nuclear & particles physics ,COUPLED-CLUSTER ,LORENTZ INTEGRAL TRANSFORM ,RESONANCE ,EFFECTIVE-FIELD THEORY ,Electric dipole moment ,Dipole ,Discrete dipole approximation codes ,RESPONSE FUNCTIONS ,Electric dipole transition ,Atomic physics - Abstract
The electric dipole polarizability quantifies the low-energy behaviour of the dipole strength and is related to critical observables such as the radii of the proton and neutron distributions. Its computation is challenging because most of the dipole strength lies in the scattering continuum. In this paper we combine integral transforms with the coupled-cluster method and compute the dipole polarizability using bound-state techniques. Employing different interactions from chiral effective field theory, we confirm the strong correlation between the dipole polarizability and the charge radius, and study its dependence on three-nucleon forces. We find good agreement with data for the 4He, 40Ca, and 16O nuclei, and predict the dipole polarizability for the rare nucleus 22O., 12 pages, 11 figures
- Published
- 2016
46. Quantum Mechanics of a Photon
- Author
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Hassan Babaei, Ali Mostafazadeh, Babaei, Hassan, Mostafazadeh, Ali (ORCID 0000-0002-0739-4060 & YÖK ID 4231), Graduate School of Sciences and Engineering, Department of Physics, and Department of Department of Mathematics
- Subjects
Physics ,Quantum Physics ,Photon ,Position operator ,Hilbert space ,FOS: Physical sciences ,Statistical and Nonlinear Physics ,01 natural sciences ,Helicity ,010305 fluids & plasmas ,symbols.namesake ,Operator (computer programming) ,Maxwell's equations ,Quantum mechanics ,Mathematical physics ,Generalized pt-symmetry ,Klein-Gordon fields ,Pseudo-hermiticity ,Position-operator ,Wave-functions ,Hilbert-space ,Cpt-symmetry ,Localizability ,Localization ,Particles ,0103 physical sciences ,symbols ,010306 general physics ,Hamiltonian (quantum mechanics) ,Wave function ,Quantum Physics (quant-ph) ,Mathematical Physics - Abstract
A first quantized free photon is a complex massless vector field $A=(A^\mu)$ whose field strength satisfies Maxwell's equations in vacuum. We construct the Hilbert space $\mathscr{H}$ of the photon by endowing the vector space of the fields $A$ in the temporal-Coulomb gauge with a positive-definite and relativistically invariant inner product. We give an explicit expression for this inner product, identify the Hamiltonian for the photon with the generator of time translations in $\mathscr{H}$, determine the operators representing the momentum and the helicity of the photon, and introduce a chirality operator whose eigenfunctions correspond to fields having a definite sign of energy. We also construct a position operator for the photon whose components commute with each other and with the chirality and helicity operators. This allows for the construction of the localized states of the photon with a definite sign of energy and helicity. We derive an explicit formula for the latter and compute the corresponding electric and magnetic fields. These turn out to diverge not just at the point where the photon is localized but on a plane containing this point. We identify the axis normal to this plane with an associated symmetry axis, and show that each choice of this axis specifies a particular position operator, a corresponding position basis, and a position representation of the quantum mechanics of photon. In particular, we examine the position wave functions determined by such a position basis, elucidate their relationship with the Riemann-Silberstein and Landau-Peierls wave functions, and give an explicit formula for the probability density of the spatial localization of the photon., Comment: 35 pages, 2 figures, slightly expanded published version
- Published
- 2016
- Full Text
- View/download PDF
47. Light-cone distribution amplitudes of the baryon octet
- Author
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R. Schiel, Meinulf Göckeler, Jakob Simeth, Vladimir M. Braun, Philipp Wein, Gunnar S. Bali, Michael Gruber, Andreas Schäfer, Fabian Hutzler, Wolfgang Söldner, and Andre Sternbeck
- Subjects
Normalization (statistics) ,Nuclear and High Energy Physics ,Particle physics ,Octet ,High Energy Physics::Lattice ,FOS: Physical sciences ,QCD SUM-RULES ,EXCLUSIVE PROCESSES ,LATTICE QCD ,ASYMPTOTIC-BEHAVIOR ,CHIRAL CORRECTIONS ,3-QUARK OPERATORS ,WAVE-FUNCTIONS ,NUCLEON ,RENORMALIZATION ,CURRENTS ,Lattice QCD ,Nonperturbative Effects ,01 natural sciences ,High Energy Physics - Phenomenology (hep-ph) ,High Energy Physics - Lattice ,Pion ,Light cone ,0103 physical sciences ,Twist ,010306 general physics ,Physics ,010308 nuclear & particles physics ,High Energy Physics - Lattice (hep-lat) ,ddc:530 ,High Energy Physics::Phenomenology ,Fermion ,530 Physik ,Baryon ,High Energy Physics - Phenomenology ,High Energy Physics::Experiment - Abstract
We present results of the first ab initio lattice QCD calculation of the normalization constants and first moments of the leading twist distribution amplitudes of the full baryon octet, corresponding to the small transverse distance limit of the associated S-wave light-cone wave functions. The P-wave (higher twist) normalization constants are evaluated as well. The calculation is done using N-f = 2 + 1 flavors of dynamical (clover) fermions on lattices of different volumes and pion masses down to 222 MeV. Significant SU(3) flavor symmetry violation effects in the shape of the distribution amplitudes are observed., SCOAP3
- Published
- 2016
- Full Text
- View/download PDF
48. Semilocal density functional theory with correct surface asymptotics
- Author
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Fabio Della Sala, José María Pitarke, Lucian A. Constantin, and Eduardo Fabiano
- Subjects
Physics ,Condensed Matter - Materials Science ,010304 chemical physics ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Electronic structure ,01 natural sciences ,Quantum chemistry ,Condensed Matter - Other Condensed Matter ,Quantum nonlocality ,Formalism (philosophy of mathematics) ,0103 physical sciences ,Density functional theory ,Statistical physics ,METAL-SURFACES ,CORRELATION-ENERGY ,EXCHANGE-ENERGY ,TUNNELING SPECTROSCOPY ,BINDING-ENERGIES ,WAVE-FUNCTIONS ,ELECTRON-GAS ,IMAGE ,APPROXIMATION ,STATES ,010306 general physics ,Other Condensed Matter (cond-mat.other) - Abstract
Semilocal density functional theory is the most used computational method for electronic structure calculations in theoretical solid-state physics and quantum chemistry of large systems, providing good accuracy with a very attractive computational cost. Nevertheless, because of the non-locality of the exchange-correlation hole outside a metal surface, it was always considered inappropriate to describe the correct surface asymptotics. Here, we derive, within the semilocal density functional theory formalism, an exact condition for the image-like surface asymptotics of both the exchange-correlation energy per particle and potential. We show that this condition can be easily incorporated into a practical computational tool, at the simple meta-generalized-gradient approximation level of theory. Using this tool, we also show that the Airy-gas model exhibits asymptotic properties that are closely related to the ones at metal surfaces. This result highlights the relevance of the linear effective potential model to the metal surface asymptotics., Comment: 6 pages, 4 figures
- Published
- 2016
49. Exploring the flexibility of MIL-47(V)-type materials using force field molecular dynamics simulations
- Author
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Louis Vanduyfhuys, Michel Waroquier, Sven Rogge, Jelle Wieme, and Veronique Van Speybroeck
- Subjects
media_common.quotation_subject ,CO2 ADSORPTION ,BASIS-SET ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Asymmetry ,Force field (chemistry) ,Damper ,Molecular dynamics ,METAL-ORGANIC FRAMEWORKS ,1ST PRINCIPLES ,WAVE-FUNCTIONS ,Physical and Theoretical Chemistry ,Wave function ,Basis set ,media_common ,Canonical ensemble ,Chemistry ,CANONICAL ENSEMBLE ,INDUCED STRUCTURAL TRANSITIONS ,Mechanics ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Shock absorber ,General Energy ,DENSITY ,0210 nano-technology ,COORDINATION POLYMERS ,MECHANICAL PRESSURE - Abstract
[Image: see text] The flexibility of three MIL-47(V)-type materials (MIL-47, COMOC-2, and COMOC-3) has been explored by constructing the pressure versus volume and free energy versus volume profiles at various temperatures ranging from 100 to 400 K. This is done with first-principles-based force fields using the recently proposed QuickFF parametrization protocol. Specific terms were added for the materials at hand to describe the asymmetry of the one-dimensional vanadium-oxide chain and to account for the flexibility of the organic linkers. The force fields are used in a series of molecular dynamics simulations at fixed volumes but varying unit cell shapes. The three materials show a distinct pressure–volume behavior, which underlines the ability to tune the mechanical properties by varying the linkers toward different applications such as nanosprings, dampers, and shock absorbers.
- Published
- 2016
- Full Text
- View/download PDF
50. A practical guide to density matrix embedding theory in quantum chemistry
- Author
-
Qiming Sun, Garnet Kin-Lic Chan, Carlos A. Jiménez-Hoyos, and Sebastian Wouters
- Subjects
Density matrix ,DIMENSIONS ,Source code ,media_common.quotation_subject ,FOS: Physical sciences ,Quantum entanglement ,01 natural sciences ,Quantum chemistry ,RENORMALIZATION-GROUP ,Theoretical physics ,SYSTEMS ,Physics - Chemical Physics ,Lattice (order) ,0103 physical sciences ,WAVE-FUNCTIONS ,Physical and Theoretical Chemistry ,010306 general physics ,Wave function ,media_common ,Physics ,Chemical Physics (physics.chem-ph) ,010304 chemical physics ,Renormalization group ,Computer Science Applications ,LATTICE ,Physics and Astronomy ,Quantum Theory ,Thermodynamics ,Embedding ,Beryllium ,Algorithms ,Hydrogen - Abstract
Density matrix embedding theory (DMET) provides a theoretical framework to treat finite fragments in the presence of a surrounding molecular or bulk environment, even when there is significant correlation or entanglement between the two. In this work, we give a practically oriented and explicit description of the numerical and theoretical formulation of DMET. We also describe in detail how to perform self-consistent DMET optimizations. We explore different embedding strategies with and without a self-consistency condition in hydrogen rings, beryllium rings, and a sample S$_{\text{N}}$2 reaction. The source code for the calculations in this work can be obtained from \url{https://github.com/sebwouters/qc-dmet}., Comment: 41 pages, 10 figures
- Published
- 2016
- Full Text
- View/download PDF
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