405 results on '"linear response function"'
Search Results
2. The linear response function as a descriptor of non-covalent interactions: hydrogen and halogen bonds.
- Author
-
Geerlings, Paul, Van Alsenoy, Christian, and De Proft, Frank
- Subjects
- *
HYDROGEN bonding interactions , *HYDROGEN bonding - Abstract
An extension of the use of the linear response function to interpret non-covalent interactions is put forward. Due to its computational intricacies, most applications until now have been done on isolated atoms or molecules using coupled perturbed Hartree–Fock or Kohn–Sham theory, thereby adopting the simplest level for the LRF evaluation, the independent particle approximation. The previously presented possibilities for extension (the random phase and the "full" expression) are scrutinised, thereby highlighting the intricacies in the evaluation of the exchange-correlation term in the case of meta-GGAs and hybrid functionals, and implemented. A set of 25 hydrogen bonded and 11 halogen bonded systems, selected from Hobza S66 and X 40 compilations, were used to investigate the correlation between the stabilisation energy due to these non-covalent interactions and the relevant atom–atom-condensed LRF matrix element. The lack of a relevant correlation in the case of hydrogen bonding is contrasted with the excellent result for the halogen bonds. The correlation between the full option and the IPA is high providing support for our previous work using the IPA as is also the case for the previously used iterative Hirshfeld condensation and the more advanced FOHI method making use of fractional occupation numbers. The fundamental difference between hydrogen and halogen bond behaviour and the retrieval of the stability sequence within the halogen bonds series are traced back to the nature of the LRF as a response function for perturbations in the external potential putting polarisation effects and the polarisability of the atoms of the donor–acceptor couple at the forefront. The extension to the use of the softness kernel is advocated and already invoked to rectify the behaviour of two deviating complexes involving S as second row halogen bond acceptor atom. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
3. The linear response function χ(r,r′): another perspective
- Author
-
Kenouche, Samir and Martínez-Araya, Jorge I.
- Published
- 2024
- Full Text
- View/download PDF
4. Constraining the Varied Response of Northern Hemisphere Winter Circulation Waviness to Climate Change.
- Author
-
Nie, Yu, Chen, Gang, Lu, Jian, Zhou, Wenyu, and Zhang, Yang
- Subjects
- *
CLIMATE change , *CLIMATE change models , *ATMOSPHERIC models , *ZONAL winds , *JET streams , *TROPICAL cyclones , *GLOBAL warming - Abstract
While a large latitudinal displacement of the westerly jet brings about disproportionate socioeconomic impacts over Northern Hemisphere midlatitude continents, it is not well understood as to whether the winter circulation will become wavier or less in response to climate change. Here, using observations and large ensembles of climate models, we show that changes in atmospheric waviness can be estimated from the optimal structures of the westerly jet for wavier circulation, which are obtained from an advection‐diffusion model. Thus, the changes in westerly jet structure in climate models under climate change provide a physical constraint on changes in atmospheric waviness, indicating that the North Atlantic wave activity will experience a robust decline in a warmer climate, while future North Pacific wave activity is obscured by model uncertainty rather than internal variability. These findings highlight the changes to jet stream structure as a constraint for regional circulation waviness in a changing climate. Plain Language Summary: A large latitudinal meandering of Northern Hemisphere winter circulation can induce stagnant weather that causes severe impacts on densely populated East Asia, Western North America, or Western Europe, yet whether the winter circulation will become wavier or less under climate change remains uncertain. Here we analyze observations and large ensembles of climate models and show that changes to atmospheric wave activity under climate change are largely constrained by changes to zonal advecting wind for the Lagrangian motion of air parcels in an advection‐diffusion model. This constraint further indicates a consistent decline in future waviness over the North Atlantic, while changes to future wave activity over the North Pacific are uncertain, due to model uncertainty rather than internal variability of the climate system. Key Points: Changes in atmospheric waviness can be roughly estimated by changes in zonal advecting wind in an advection‐diffusion modelChanges in the optimal structure of jet stream help constrain regional circulation waviness in a changing climateModel results suggest future waviness will robustly decline in North Atlantic but is less clear in North Pacific due to model uncertainty [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
5. Constraining the Varied Response of Northern Hemisphere Winter Circulation Waviness to Climate Change
- Author
-
Yu Nie, Gang Chen, Jian Lu, Wenyu Zhou, and Yang Zhang
- Subjects
circulation waviness ,physical constraint ,optimal jet structure ,linear response function ,climate change ,Geophysics. Cosmic physics ,QC801-809 - Abstract
Abstract While a large latitudinal displacement of the westerly jet brings about disproportionate socioeconomic impacts over Northern Hemisphere midlatitude continents, it is not well understood as to whether the winter circulation will become wavier or less in response to climate change. Here, using observations and large ensembles of climate models, we show that changes in atmospheric waviness can be estimated from the optimal structures of the westerly jet for wavier circulation, which are obtained from an advection‐diffusion model. Thus, the changes in westerly jet structure in climate models under climate change provide a physical constraint on changes in atmospheric waviness, indicating that the North Atlantic wave activity will experience a robust decline in a warmer climate, while future North Pacific wave activity is obscured by model uncertainty rather than internal variability. These findings highlight the changes to jet stream structure as a constraint for regional circulation waviness in a changing climate.
- Published
- 2023
- Full Text
- View/download PDF
6. Characterizing Convection Schemes Using Their Responses to Imposed Tendency Perturbations
- Author
-
Y. L. Hwong, S. Song, S. C. Sherwood, A. J. Stirling, C. Rio, R. Roehrig, C. L. Daleu, R. S. Plant, D. Fuchs, P. Maher, and L. Touzé‐Peiffer
- Subjects
convection ,convective parameterization ,idealized model ,linear response function ,radiative‐convective equilibrium ,SCM ,Physical geography ,GB3-5030 ,Oceanography ,GC1-1581 - Abstract
Abstract Convection is usually parameterized in global climate models, and there are often large discrepancies between results obtained with different convection schemes. Conventional methods of comparing convection schemes using observational cases or directly in three‐dimensional (3D) models do not always clearly identify parameterization strengths and weaknesses. In this paper we evaluate the response of parameterizations to various perturbations rather than their behavior under particular strong forcing. We use the linear response function method proposed by Kuang (2010) to compare 12 physical packages in five atmospheric models using single‐column model (SCM) simulations under idealized radiative‐convective equilibrium conditions. The models are forced with anomalous temperature and moisture tendencies. The temperature and moisture departures from equilibrium are compared with published results from a cloud‐resolving model (CRM). Results show that the procedure is capable of isolating the behavior of a convection scheme from other physics schemes. We identify areas of agreement but also substantial differences between convection schemes, some of which can be related to scheme design. Some aspects of the model linear responses are related to their RCE profiles (the relative humidity profile in particular), while others constitute independent diagnostics. All the SCMs show irregularities or discontinuities in behavior that are likely related to threshold‐related mechanisms used in the convection schemes, and which do not appear in the CRM. Our results highlight potential flaws in convection schemes and suggest possible new directions to explore for parameterization evaluation.
- Published
- 2021
- Full Text
- View/download PDF
7. The density polarization reveals directions of electron displacements due to the substituent effect: Analysis performed on a metal‐organic Mo‐Oxo catalyst.
- Author
-
Martínez‐Araya, Jorge I. and Morell, Christophe
- Subjects
- *
ACTIVATION energy , *MOLECULAR structure , *MOLE fraction , *ELECTRONS , *DENSITY , *ELECTRON density , *MOLYBDENUM ions - Abstract
Some Mo‐oxo complexes bearing pyridine rings have the capability for dihydrogen production from water. However, energy barrier and overall energy vary depending on the effect exerted by several substituent groups located at different positions around one or more pyridine rings which are ligands of these compounds. Based on the Karunadasa and coworkers investigation where the para‐position was experimentally tested in compounds derivatised from the 2,6‐bis[1,1‐bis(2‐pyridil)ethyl]‐pyridine oxo‐molybdenum complex synthesized (Karunadasa et al., Nature, 2010, 464, 1329), we tested the combined effect of electron‐withdrawing and electron‐donating groups simulated as perturbations represented by point‐charges. Then, we used the density polarization concept, δρ(r), a local reactivity descriptor corresponding to the partially integrated linear response function, χ(r, r′) (a non‐local reactivity descriptor), which is able to reveal different displacements of π‐electrons on molecular structures. We perturbed the para‐positions in the pentadentate ligand 2,6‐bis[1,1‐bis(2‐pyridil)ethyl]‐pyridine in the Mo‐based complex by means of point‐charges. They were located in three different configurations of the organic ligand (trans, geminal, and cis) which could help to explain energy barriers and overall energy of reactions catalyzed by this type of Mo‐complexes. Our results indicate that the trans configuration of point‐charges induces the most amount of fraction of electron shifted on the complex. A Mo‐based complex bearing the same trans configuration for electron‐withdrawing and electron‐donating substituent groups (cyano and amino, respectively), leads to a kinetically more favorable H2 release than the cis or geminal configuration of the substituent groups aforementioned. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
8. Characterizing Convection Schemes Using Their Responses to Imposed Tendency Perturbations.
- Author
-
Hwong, Y. L., Song, S., Sherwood, S. C., Stirling, A. J., Rio, C., Roehrig, R., Daleu, C. L., Plant, R. S., Fuchs, D., Maher, P., and Touzé‐Peiffer, L.
- Subjects
- *
ATMOSPHERIC models , *HEAT convection , *HUMIDITY , *BOUNDARY layer (Aerodynamics) , *SUPPLY chain management - Abstract
Convection is usually parameterized in global climate models, and there are often large discrepancies between results obtained with different convection schemes. Conventional methods of comparing convection schemes using observational cases or directly in three‐dimensional (3D) models do not always clearly identify parameterization strengths and weaknesses. In this paper we evaluate the response of parameterizations to various perturbations rather than their behavior under particular strong forcing. We use the linear response function method proposed by Kuang (2010) to compare 12 physical packages in five atmospheric models using single‐column model (SCM) simulations under idealized radiative‐convective equilibrium conditions. The models are forced with anomalous temperature and moisture tendencies. The temperature and moisture departures from equilibrium are compared with published results from a cloud‐resolving model (CRM). Results show that the procedure is capable of isolating the behavior of a convection scheme from other physics schemes. We identify areas of agreement but also substantial differences between convection schemes, some of which can be related to scheme design. Some aspects of the model linear responses are related to their RCE profiles (the relative humidity profile in particular), while others constitute independent diagnostics. All the SCMs show irregularities or discontinuities in behavior that are likely related to threshold‐related mechanisms used in the convection schemes, and which do not appear in the CRM. Our results highlight potential flaws in convection schemes and suggest possible new directions to explore for parameterization evaluation. Plain Language Summary: The transport of heat up and down the atmosphere, called atmospheric convection, is a complex process. To simplify the representation of convection in global climate models (GCMs) scientists use "parameterization," which is essentially mathematical equations of physical processes. However, there are many different ways to formulate these equations, and no agreement on which is better. In this work we aim to understand a few popular ways to parameterize convection. We extract one vertical column from five different GCMs and lightly tickle (perturb) it and then observe its responses. We found that different models respond very differently to the same tickling, and this tells us a lot about the model. Importantly, the specific perturbation that we used can single out the responses of convection‐related equations from equations of other processes. All the models in our study have one thing in common: They are quite jumpy when tickled, especially at the top of the boundary layer where clouds start to form. We suspect the culprits are thresholds placed in the models that sometimes lead to sudden changes in their response. Our work highlights potentially problematic behavior that can give clues on how to make climate models better. Key Points: The linear response function method is applied in single‐column model (SCM) simulations and is able to isolate the behavior of convection schemesLinear responses of the models are related to the mean state relative humidity in both shape and magnitudeAll SCMs show discontinuities in their responses which are likely related to thresholds used in convective parameterization [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
9. Dissipative quantum dynamics
- Author
-
Schröter, Marco and Schröter, Marco
- Published
- 2015
- Full Text
- View/download PDF
10. Excitation Energies and Transition Moments from the PCM Linear Response Functions
- Author
-
Cammi, Roberto and Cammi, Roberto
- Published
- 2013
- Full Text
- View/download PDF
11. Responses to auxin signals: an operating principle for dynamical sensitivity yet high resilience
- Author
-
S. Grigolon, B. Bravi, and O. C. Martin
- Subjects
signalling networks ,operating principles ,linear response function ,Science - Abstract
Plants depend on the signalling of the phytohormone auxin for their development and for responding to environmental perturbations. The associated biomolecular signalling network involves a negative feedback on Aux/IAA proteins which mediate the influence of auxin (the signal) on the auxin response factor (ARF) transcription factors (the drivers of the response). To probe the role of this feedback, we consider alternative in silico signalling networks implementing different operating principles. By a comparative analysis, we find that the presence of a negative feedback allows the system to have a far larger sensitivity in its dynamical response to auxin and that this sensitivity does not prevent the system from being highly resilient. Given this insight, we build a new biomolecular signalling model for quantitatively describing such Aux/IAA and ARF responses.
- Published
- 2018
- Full Text
- View/download PDF
12. Driving a Laser Oscillation
- Author
-
Renk, Karl F. and Renk, Karl F.
- Published
- 2012
- Full Text
- View/download PDF
13. Beyond the Runge–Gross Theorem
- Author
-
Ruggenthaler, Michael, van Leeuwen, Robert, Marques, Miguel A.L., editor, Maitra, Neepa T., editor, Nogueira, Fernando M.S., editor, Gross, E.K.U., editor, and Rubio, Angel, editor
- Published
- 2012
- Full Text
- View/download PDF
14. Response Functions in TDDFT: Concepts and Implementation
- Author
-
Strubbe, David A., Lehtovaara, Lauri, Rubio, Angel, Marques, Miguel A. L., Louie, Steven G., Marques, Miguel A.L., editor, Maitra, Neepa T., editor, Nogueira, Fernando M.S., editor, Gross, E.K.U., editor, and Rubio, Angel, editor
- Published
- 2012
- Full Text
- View/download PDF
15. Exact Conditions and Their Relevance in TDDFT
- Author
-
Wagner, Lucas O., Yang, Zeng-hui, Burke, Kieron, Marques, Miguel A.L., editor, Maitra, Neepa T., editor, Nogueira, Fernando M.S., editor, Gross, E.K.U., editor, and Rubio, Angel, editor
- Published
- 2012
- Full Text
- View/download PDF
16. Cumulant Corrections in Turbulence : Quasinormal Approximation, Direct Interaction Approximation, and Non-Gaussian Properties of Turbulence
- Author
-
Rubinstein, Robert, Bos, Wouter J. T., Oberlack, Martin, editor, Peinke, Joachim, editor, Talamelli, Alessandro, editor, Castillo, Luciano, editor, and Hölling, Michael, editor
- Published
- 2012
- Full Text
- View/download PDF
17. Identification of linear response functions from arbitrary perturbation experiments in the presence of noise – Part 1: Method development and toy model demonstration
- Author
-
G. L. Torres Mendonça, J. Pongratz, and C. H. Reick
- Subjects
Toy model ,QC801-809 ,Computer science ,Science ,Physics ,QC1-999 ,Geophysics. Cosmic physics ,Monotonic function ,Linear response function ,Regularization (mathematics) ,Background noise ,Nonlinear system ,Noise ,Robustness (computer science) ,Applied mathematics - Abstract
Existent methods to identify linear response functions from data require tailored perturbation experiments, e.g., impulse or step experiments, and if the system is noisy, these experiments need to be repeated several times to obtain good statistics. In contrast, for the method developed here, data from only a single perturbation experiment at arbitrary perturbation are sufficient if in addition data from an unperturbed (control) experiment are available. To identify the linear response function for this ill-posed problem, we invoke regularization theory. The main novelty of our method lies in the determination of the level of background noise needed for a proper estimation of the regularization parameter: this is achieved by comparing the frequency spectrum of the perturbation experiment with that of the additional control experiment. The resulting noise-level estimate can be further improved for linear response functions known to be monotonic. The robustness of our method and its advantages are investigated by means of a toy model. We discuss in detail the dependence of the identified response function on the quality of the data (signal-to-noise ratio) and on possible nonlinear contributions to the response. The method development presented here prepares in particular for the identification of carbon cycle response functions in Part 2 of this study (Torres Mendonça et al., 2021a). However, the core of our method, namely our new approach to obtaining the noise level for a proper estimation of the regularization parameter, may find applications in also solving other types of linear ill-posed problems.
- Published
- 2021
18. Ab Initio Calculation of Li-Sn System: Unraveling New Phases of Superconducting Materials with Increasing Compression
- Author
-
Thong Leng Lim, S. K. Lai, Tiem Leong Yoon, and Yee Hui Robin Chang
- Subjects
Superconductivity ,Crystal ,symbols.namesake ,Materials science ,Condensed matter physics ,Fermi level ,Ab initio ,symbols ,Tetrahedron ,Density functional theory ,Soft modes ,Linear response function - Abstract
Stoichiometry, crystal compound, electronic attributes and superconductivity of compressed lithium-tin composites have been thoroughly studied using quantum mechanical genetic algorithm approach and the first principles computations based on density functional theory. Our simulations at moderate pressure (5-20 GPa) predict a complex convex hull diagram, with the following stable Li‑rich phases: I4/mmm-Li6Sn2, -Li7Sn2, -Li5Sn2, Ama2-Li4Sn2, -Li5Sn2, -Li6Sn2, C2/m-Li4Sn1, P21/m-Li6Sn2, -Li7Sn2 and Cmcm-Li4Sn2. Careful examination at their independent elastic parameters reveals sufficient mechanical stability in them. These phases are metallic system, with reasonably high electron concentration near to Fermi level or N(EF) that ranges from 0.6 to 2.4 states/eV cell. It is also interesting for us to observe soft modes and steep-flat energy bands at Fermi levels of Li6Sn2 structures which are stable throughout the pressure range. These features are prerequisites for superconducting behavior. Linear response function with Gaussian and tetrahedron methods reveals satisfactory superconducting transition temperature Tc (3.1 ~ 6.6 K) and Tc (2.1 ~ 2.4 K), respectively. Structural transition results for based elements Li and Sn agree well with literature thus signifying reliable prediction of intermediate phases.
- Published
- 2021
19. A reference‐free stockholder partitioning method based on the force on electrons.
- Author
-
Fias, Stijn, Heidar‐Zadeh, Farnaz, Anderson, James S. M., Ayers, Paul W., and Parr, Robert G.
- Subjects
- *
ELECTRON density , *ATOMIC nucleus , *GROUND state (Quantum mechanics) , *EHRENFEST'S theorem , *DENSITY functional theory - Abstract
We argue that when one divides a molecular property into atom‐in‐a‐molecule contributions, one should perform the division based on the property density of the quantity being partitioned. This is opposition to the normal approach, where the electron density is given a privileged role in defining the properties of atoms‐in‐a‐molecule. Because partitioning each molecular property based on its own property density is inconvenient, we design a reference‐free approach that does not (directly) refer atomic property densities. Specifically, we propose a stockholder partitioning method based on relative influence of a molecule's atomic nuclei on the electrons at a given point in space. The resulting method does not depend on an “arbitrary” choice of reference atoms and it has some favorable properties, including the fact that all of the electron density at an atomic nucleus is assigned to that nucleus and the fact all the atoms in a molecule decay at a uniform asymptotic rate. Unfortunately, the resulting model is not easily applied to spatially degenerate ground states. Furthermore, the practical realizations of this strategy that we tried here gave disappointing numerical results. © 2017 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
20. The Dielectric Response Functions
- Author
-
Kuzmany, Hans and Kuzmany, Hans
- Published
- 2009
- Full Text
- View/download PDF
21. Linear Response Theory in Connection to Density Functional Theory/Molecular Dynamics and Coupled Cluster/Molecular Dynamics Methods
- Author
-
Aidas, Kestutis, Kongsted, Jacob, Mikkelsen, Kurt V., and Canuto, Sylvio, editor
- Published
- 2008
- Full Text
- View/download PDF
22. Kohn–Sham Time-Dependent Density Functional Theory with Applications to Linear and Nonlinear Properties
- Author
-
Jonsson, Dan, Vahtras, Olav, Jansik, Branislav, Rinkevicius, Zilvinas, Sałek, Paweł, Ågren, Hans, Leszczynski, Jerzy, editor, Papadopoulos, Manthos G., editor, and Sadlej, Andrzej J., editor
- Published
- 2006
- Full Text
- View/download PDF
23. Beyond the Runge-Gross Theorem
- Author
-
van Leeuwen, R., Beig, R., editor, Beiglböck, W., editor, Domcke, W., editor, Englert, B.-G., editor, Frisch, U., editor, Hänggi, P., editor, Hasinger, G., editor, Hepp, K., editor, Hillebrandt, W., editor, Imboden, D., editor, Jaffe, R. L., editor, Lipowsky, R., editor, Löhneysen, H. v., editor, Ojima, I., editor, Sornette, D., editor, Theisen, S., editor, Weise, W., editor, Wess, J., editor, Zittartz, J., editor, Marques, Miguel A.L., editor, Ullrich, Carsten A., editor, Nogueira, Fernando, editor, Rubio, Angel, editor, Burke, Kieron, editor, and Gross, Eberhard K. U., editor
- Published
- 2006
- Full Text
- View/download PDF
24. Theoretical Investigation on Nearsightedness of Finite Model and Molecular Systems Based on Linear Response Function Analysis
- Author
-
Yuki Mitsuta, Shusuke Yamanaka, Kizashi Yamaguchi, Mitsutaka Okumura, and Haruki Nakamura
- Subjects
nearsightedness of electronic matter ,linear response function ,finite systems ,Organic chemistry ,QD241-441 - Abstract
We examined nearsightedness of electronic matter (NEM) of finite systems on the basis of linear response function (LRF). From the computational results of a square-well model system, the behavior of responses obviously depends on the number of electrons (N): as N increases, LRF, δρ(r)/δv(r′), decays rapidly for the distance, |r−r′|. This exemplifies that the principle suggested by Kohn and Prodan holds even for finite systems: the cause of NEM is destructive interference among electron density amplitudes. In addition, we examined double-well model systems, which have low-lying degenerate levels. In this case, there are two types of LRF: the cases of the half-filled and of full-filled in low-lying degenerate levels. The response for the former is delocalized, while that of the later is localized. These behaviors of model systems are discussed in relation to the molecular systems’ counterparts, H2, He22+, and He2 systems. We also see that NEM holds for the dissociated limit of H2, of which the mechanism is similar to that of the insulating state of solids as suggested by Kohn. We also examined LRF of alanine tripeptide system as well as butane and butadiene molecules, showing that NEM of the polypeptide system is caused by sp3 junctions at Cα atoms that prevent propagation of amplitudes of LRF, which is critically different from that of NEM for finite and infinite homogeneous systems.
- Published
- 2014
- Full Text
- View/download PDF
25. The density polarization reveals directions of electron displacements due to the substituent effect: Analysis performed on a metal‐organic Mo‐Oxo catalyst
- Author
-
Christophe Morell, Jorge Ignacio Martínez-Araya, Universidad Andrés Bello [Santiago] (UNAB), Chemometrics and Theoretical Chemistry - Chimiométrie et chimie théorique, Institut des Sciences Analytiques (ISA), Institut de Chimie du CNRS (INC)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), and Fondo Nacional de Desarrollo Cientifico y Tecnologico, Grant/Award Number: 1181504
- Subjects
metal ,Conceptual Density ,Substituent ,010402 general chemistry ,01 natural sciences ,Catalysis ,chemistry.chemical_compound ,0103 physical sciences ,Pyridine ,[CHIM]Chemical Sciences ,Reactivity (chemistry) ,density polarization ,Polarization (electrochemistry) ,organic Mo-oxo complexes ,ComputingMilieux_MISCELLANEOUS ,mesomeric effect ,010304 chemical physics ,Geminal ,Ligand ,linear response function ,General Chemistry ,Mesomeric effect ,0104 chemical sciences ,[CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry ,Computational Mathematics ,Crystallography ,chemistry ,Functional Theory ,substituent effect - Abstract
Some Mo-oxo complexes bearing pyridine rings have the capability for dihydrogen production from water. However, energy barrier and overall energy vary depending on the effect exerted by several substituent groups located at different positions around one or more pyridine rings which are ligands of these compounds. Based on the Karunadasa and coworkers investigation where the para-position was experimentally tested in compounds derivatised from the 2,6-bis[1,1-bis(2-pyridil)ethyl]-pyridine oxo-molybdenum complex synthesized (Karunadasa et al., Nature, 2010, 464, 1329), we tested the combined effect of electron-withdrawing and electron-donating groups simulated as perturbations represented by point-charges. Then, we used the density polarization concept, δρ(r), a local reactivity descriptor corresponding to the partially integrated linear response function, χ(r, r') (a non-local reactivity descriptor), which is able to reveal different displacements of π-electrons on molecular structures. We perturbed the para-positions in the pentadentate ligand 2,6-bis[1,1-bis(2-pyridil)ethyl]-pyridine in the Mo-based complex by means of point-charges. They were located in three different configurations of the organic ligand (trans, geminal, and cis) which could help to explain energy barriers and overall energy of reactions catalyzed by this type of Mo-complexes. Our results indicate that the trans configuration of point-charges induces the most amount of fraction of electron shifted on the complex. A Mo-based complex bearing the same trans configuration for electron-withdrawing and electron-donating substituent groups (cyano and amino, respectively), leads to a kinetically more favorable H2 release than the cis or geminal configuration of the substituent groups aforementioned.
- Published
- 2021
26. Linear Response Functions of Densities and Spin Densities for Systematic Modeling of the QM/MM Approach for Mono- and Poly-Nuclear Transition Metal Systems
- Author
-
Colin K. Kitakawa, Tomohiro Maruyama, Jinta Oonari, Yuki Mitsuta, Takashi Kawakami, Mitsutaka Okumura, Kizashi Yamaguchi, and Shusuke Yamanaka
- Subjects
linear response function ,QM/MM ,transition metal complexes ,enzymes ,Organic chemistry ,QD241-441 - Abstract
We applied our analysis, based on a linear response function of density and spin density, to two typical transition metal complex systems-the reaction centers of P450, and oxygen evolving center in Photosystem II, both of which contain open-shell transition metal ions. We discuss the relationship between LRF of electron density and spin density and the types of units and interactions of the systems. The computational results are discussed in relation to quantum mechanics (QM) cluster and quantum mechanics/molecular mechanics (QM/MM) modeling that are employed to compute the reaction centers of enzymes.
- Published
- 2019
- Full Text
- View/download PDF
27. Orbital-Free Kinetic-Energy Density Functional Theory
- Author
-
Wang, Yan Alexander, Carter, Emily A., Lipscomb, W. N., editor, Prigogine, I., editor, and Schwartz, Steven D., editor
- Published
- 2002
- Full Text
- View/download PDF
28. Linear Response Function of Bond-Order.
- Author
-
Nayuta Suzuki, Yuki Mitsuta, Mitsutaka Okumura, and Shusuke Yamanaka
- Subjects
- *
BOND order (Chemistry) , *ACIDS , *CHEMICAL reactions , *BENZOATES , *INDUCTIVE effect , *COMPUTATIONAL chemistry , *QUANTUM perturbations - Abstract
We present the linear response function of bond-orders (LRF-BO) based on a real space integration scheme for molecular systems. As in the case of the LRF of density, the LRF-BO is defined as the response of the bond order of the molecule for the virtual perturbation. Our calculations show that the LRF-BO enables us not only to detect inductive and resonating effects of conjugating systems, but also to predict pKa values on substitution groups via linear relationships between the Hammett constants and the LRF-BO values for meta- and para-substituted benzoic acids. More importantly, the LRF-BO values for the O-H bonds strongly depend on the sites to which the virtual perturbation is applied, implying that the LRF-BO values include essential information about reaction mechanism of the acid-dissociation of substituted benzoic acids. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
29. Can We Use 1D Models to Predict 3D Model Response to Forcing in an Idealized Framework?
- Author
-
Hwong, Yi-Ling, Sherwood, Steven C., and Fuchs, David
- Subjects
Global and Planetary Change ,convective parameterization ,climate change ,linear response function ,General Earth and Planetary Sciences ,Environmental Chemistry ,atmospheric modelling ,doubled-CO2 ,single-column models ,multi-column models ,radiative-convective equilibrium - Abstract
This repository contains the data, scripts, WRF codes and filesrequired to reproduce the results of the manuscript"Can We Use 1D Models to Predict 3D Model Response to Forcing in an Idealized Framework?" submitted to the Journal of Advances in Modeling Earth Systems (JAMES). Brief description of project This project aims to examine the comparability of results obtained using a 1D (or single-column model, SCM) versus 3D model under radiative-convective equilibrium (RCE) conditions. Simulations are carried out with the Weather Research and Forecasting (WRF) model (version 4.0.2). A 20 x 20 Multi-column model (MCM) setup is used as a stepping stone for the 3D model. The comparability of the SCM and MCM results is assessed based on their mean states, linear responses to small tendency perturbations (following the linear response function framework of Kuang, 2010), and adjustment responsesto a doubled-CO2 forcing. Five widely used convection schemes are tested: Kain-Fritsch New-Tiedtke New-simplified Arakawa-Schubert Betts-Miller-Janjic Zhang-McFarlane The default WRF code base (version 4.0.2) can be downloaded from here:https://github.com/coecms/WRF/tree/V4.0.2/WRFV3 Repository structure /WRF4.0.2 directory: contains the WRF fortran code and run time files required to conduct the simulations described in the manuscript /WRF4.0.2/WRFV3: contains the modified fortran code for the various experimental configurations /WRF4.0.2/runtime: contains the run time files required to run the SCM and MCM experiments (namelists, sst_hotspot_input, input_sounding, etc) /data directory: contains the model output data, in csv format /data/anomalies: contains the T and q responses to dT and dq tendency perturbations /data/double_co2: contains the doubled-CO2 forcing adjustment responses /data/matrices: contains the X and dX matrices of the five convection schemes in SCM, which are required toconstruct their M-1 matrices /data/mean_states: contains the T and RH mean state of the schemes /data/precip: contains the convective and large-scale rain data, as well as the data for rainfall PDFs /data/pressures: contains the pressure levels of the five convection schemes /data/pw: contains the precipitable water data required to plot the org_pw metric time series /data/subsidence: contains the vertical wind velocity (W) values required to compute the subsidence fraction metric /data/dataframes: contains the dataframe files for statistical analyses (linear mixed effects [lme] models) /scripts directory: contains the scripts required to plot all figures in the manuscript plot_convective_rain.py: script to plot Figures 1 and 2 (daily accumulated convective rain) plot_org_time_series.py: script to plot Figure 3 (time series of the org_pw metric) plot_mean_state_mcm.py: script to plot Figure 4 (T and RH mean state for the MCM setup and for all experimental configurations) plot_scm_mcm_mean_state_difference.py: script to plot Figure 5 (T and RH difference between the SCM and MCM for the organized and disorganized cases) plot_rain_pdf_scm_mcm_daily.py: script to plot Figure 6 (PDFs of daily convective rain of SCM vs MCM) plot_lrf_response_scm_mcm_org_disorg.py: script to plot Figures 7and 8(SCM vs. MCM T and q responses to small tendency perturbations) plot_scatter_plot_org_vs_various.py: script to plot Figure 9(scatter plots of org_pw vs. RH and org_pw vs. SCM-MCM-deviation) plot_scatter_plot_scm_mcm_relative_difference.py: script to plot Figure 10(scatter plots of SCM-pair-difference vs. MCM-pair-difference for the organized and disorganized cases) plot_double_co2_response_scm_mcm.py: script to plot Figure 11(comparison of SCM vs. MCM adjustments to doubled-CO2 forcing) plot_double_co2_response_sim_pred.py: script to plot Figure 12 (comparison of simulated vs. predicted adjustment responses to doubled-CO2 forcing) plot_M_inv_matrices.py: script to plot Figure A1(M-1 matrices of the five convection schemes in SCM setup) /scripts/applications directory: contains the utilities script that include helper functions for the plotting scripts
- Published
- 2022
- Full Text
- View/download PDF
30. The Dielectric Function
- Author
-
Kuzmany, Hans and Kuzmany, Hans
- Published
- 1998
- Full Text
- View/download PDF
31. The Representation of Facts in Physical Theories
- Author
-
Primas, Hans, Atmanspacher, Harald, editor, and Ruhnau, Eva, editor
- Published
- 1997
- Full Text
- View/download PDF
32. Density Estimation by Maximum Quantum Entropy
- Author
-
Silver, R. N., Wallstrom, T., Martz, H. F., Van Der Merwe, Alwyn, editor, and Heidbreder, Glenn R., editor
- Published
- 1996
- Full Text
- View/download PDF
33. Quantum Brownian Oscillator Analysis of Pump-Probe Spectroscopy in the Condensed Phase
- Author
-
Tanimura, Yoshitaka, Mukamel, Shaul, Truhlar, Donald G., editor, and Simon, John D., editor
- Published
- 1994
- Full Text
- View/download PDF
34. Symmetry-Adapted Perturbation Theory Based on Multiconfigurational Wave Function Description of Monomers
- Author
-
Michał Hapka, Michał Przybytek, and Katarzyna Pernal
- Subjects
Physics ,Field (physics) ,Linear response function ,Molecular physics ,Article ,Computer Science Applications ,Excited state ,Physics::Atomic and Molecular Clusters ,Complete active space ,Physical and Theoretical Chemistry ,Perturbation theory ,Random phase approximation ,Wave function ,Generalized valence bond - Abstract
We present a formulation of the multiconfigurational (MC) wave function symmetry-adapted perturbation theory (SAPT). The method is applicable to noncovalent interactions between monomers which require a multiconfigurational description, in particular when the interacting system is strongly correlated or in an electronically excited state. SAPT(MC) is based on one- and two-particle reduced density matrices of the monomers and assumes the single-exchange approximation for the exchange energy contributions. Second-order terms are expressed through response properties from extended random phase approximation (ERPA). The dispersion components of SAPT(MC) have been introduced in our previous works [HapkaM.J. Chem. Theory Comput.2019, 15, 1016−102730525591; HapkaM.J. Chem. Theory Comput.2019, 15, 6712–672331670950]. SAPT(MC) is applied either with generalized valence bond perfect pairing (GVB) or with complete active space self-consistent field (CASSCF) treatment of the monomers. We discuss two model multireference systems: the H2 ··· H2 dimer in out-of-equilibrium geometries and interaction between the argon atom and excited state of ethylene. Using the C2H4* ··· Ar complex as an example, we examine second-order terms arising from negative transitions in the linear response function of an excited monomer. We demonstrate that the negative-transition terms must be accounted for to ensure qualitative prediction of induction and dispersion energies and develop a procedure allowing for their computation. Factors limiting the accuracy of SAPT(MC) are discussed in comparison with other second-order SAPT schemes on a data set of small single-reference dimers.
- Published
- 2021
35. Can We Use 1D Models to Predict 3D Physics?
- Author
-
David Fuchs, Y L Hwong, and Steven C. Sherwood
- Subjects
business.industry ,linear response function ,Machine learning ,computer.software_genre ,doubled-CO2 ,convective parameterization ,climate change ,Artificial intelligence ,atmospheric modelling ,business ,computer ,single-column models ,multi-column models ,radiative-convective equilibrium - Abstract
This repository contains the data and scripts required to reproduce the results of the manuscript"Can We Use 1D Models to Predict 3D Physics?" submitted to the Journal of Advances in Modeling Earth Systems (JAMES). Brief description of project This project aims to examine the comparability of results obtained using a 1D (or single-column model, SCM) versus 3D model under radiative-convective equilibrium (RCE) conditions. Simulations are carried out with the Weather Research and Forecasting (WRF) model (version 4.0.2). A 20 x 20 Multi-column model (MCM) setup is used as a stepping stone for the 3D model. The comparability of the SCM and MCM results is assessed based on their mean states, linear responses to small tendency perturbations (following the linear response function framework of Kuang, 2010), and adjustment responsesto a doubled-CO2 forcing. Five widely used convection schemes are tested: Kain-Fritsch New-Tiedtke New-simplified Arakawa-Schubert Betts-Miller-Janjic Zhang-McFarlane Repository structure /data directory: contains the model outputs, in csv format /data/anomalies directory: contains the T and q responses to dT and dq tendency perturbations /data/double_co2: contains the doubled-CO2 forcing adjustment responses /data/matrices: contains the X and dX matrices of the five convection schemes in SCM, which are required toconstruct their M-1 matrices /data/mean_states: contains the T and RH mean state of the schemes /data/precip: contains the convective and large-scale rain data /data/pressures: contains the pressure levels of the five convection schemes /data/pw: contains the precipitable water data required to plot the org_pw metric time series /data/subsidence: contains the vertical wind velocity (W) values required to compute the subsidence fraction metric /scripts directory: contains the scripts required to plot all figures in the manuscript plot_convective_rain.py: script to plot Figures 1 and 2 (daily accumulated convective rain) plot_org_time_series.py: script to plot Figure 3 (time series of the org_pw metric) plot_mean_state_mcm.py: script to plot Figure 4 (T and RH mean state for the MCM setup and for all experimental configurations) plot_scm_mcm_mean_state_difference.py: script to plot Figure 5 (T and RH difference between the SCM and MCM for the organized and disorganized cases) plot_lrf_response_scm_mcm_org_disorg.py: script to plot Figures 6 and 7 (SCM vs. MCM T and q responses to small tendency perturbations) plot_scatter_plot_org_vs_various.py: script to plot Figure 8 (scatter plots of org_pw vs. RH and org_pw vs. SCM-MCM-deviation) plot_scatter_plot_scm_mcm_relative_difference.py: script to plot Figure 9 (scatter plots of SCM-pair-difference vs. MCM-pair-difference for the organized and disorganized cases) plot_double_co2_response_scm_mcm.py: script to plot Figure 10 (comparison of SCM vs. MCM adjustments to doubled-CO2 forcing) plot_M_inv_matrices.py: script to plot Figure 11 (M-1 matrices of the five convection schemes in SCM setup) plot_double_co2_response_sim_pred.py: script to plot Figure 12 (comparison of simulated vs. predicted adjustment responses to doubled-CO2 forcing) /scripts/applications directory: contains the utilities script that include helper functions for the plotting scripts
- Published
- 2021
- Full Text
- View/download PDF
36. Linear Response Function Reveals the Most Effective Remote Forcing in Causing September Arctic Sea Ice Melting in CESM
- Author
-
Qinghua Ding, Fukai Liu, Yutian Wu, and Jian Lu
- Subjects
geography ,Geophysics ,geography.geographical_feature_category ,Climatology ,Sea ice ,General Earth and Planetary Sciences ,Environmental science ,Forcing (mathematics) ,Linear response function ,Arctic ice pack - Published
- 2021
37. The E = E[N, v] functional and the linear response function: a conceptual DFT viewpoint.
- Author
-
Geerlings, Paul, Boisdenghien, Zino, Proft, Frank De, and Fias, Stijn
- Subjects
- *
NUCLEAR optical models , *ELECTRON impact ionization , *IONIZATION energy , *ELECTRON density , *ELECTRON affinity , *DENSITY functional theory , *GENERATING functions - Abstract
The energy (E) versus number of electrons (N) and external potential (v) functional E = E[N, v], which has proved to be of fundamental importance in conceptual density functional theory through the response functions it generates, has been examined concentrating on the concavity of the E = E[v] functional as opposed to the convexity of the E = E(N) function. The concavity of the E = E[v] functional is reflected in negative values of the diagonal elements of the linear response function χ (r , r ′) comprising the second functional derivative of E with respect to v (r) , whereas no sign can be retrieved for the off-diagonal elements. These findings are in agreement with recent computational studies in extracting the chemical content of the linear response function. The results for the diagonal elements can easily be interpreted in terms of electron depletion from regions where the potential is increased and are easily retrieved via the independent particle model expression and in agreement with the diagonal elements of the most general expression for the linear response function. These concavity-related issues are put in contrast with the positive (∂ 2 E / ∂ N 2) v derivative, resulting from the convexity of the E(N) function, in line with the positivity of the chemical hardness as resulting from the I versus A (ionization vs. electron affinity) ratio. The first-order derivative (δ E / δ v (r)) N is discussed within an iso-electronic atom series for which it is shown in detail that the potentials can be ordered univocally, through their Z-dependence. The sign of the slope of the E = E[v] curve is in agreement with the positivity of ρ (r) . The result for the E = E[v] functional is put in contrast with the negative (∂ E / ∂ N) v derivative (identified as minus the electronegativity) for the E = E(N) function retrieved on the basis of experimental and theoretical data on ionization energies and electron affinities. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
38. Nearsightedness-related indices of finite systems based on linear response function: one-dimensional cases.
- Author
-
Mitsuta, Yuki, Yamanaka, Shusuke, Saito, Toru, Kawakami, Takashi, Yamaguchi, Kizashi, Okumura, Mitsutaka, and Nakamura, Haruki
- Subjects
- *
ELECTRONIC materials , *QUANTUM mechanics , *LINEAR systems , *COMPUTATIONAL chemistry , *PARTICLE dynamics analysis - Abstract
We have investigated nearsightedness of electronic matter (NEM) of finite systems on the basis of linear response function to examine theoretical foundation of contemporary computational chemistry such as quantum mechanics/molecular mechanics methods. In this study, we introduce several nearsightedness-related indices to assess the magnitude of localisability of responses for one-dimensional finite model systems. We started from two electrons' systems, which are beyond the scope of the original concept of NEM, and increased the number of electrons (N) to a hundred electrons to analyse dependency of such indices onN. In the process of construction of the indices, we analysed the factors, because of which the magnitude of nonlocal parts of linear response functions becomes small, into several ones, and extracted purely the magnitude of propagation of responses. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
39. Electron Spectra in Solids
- Author
-
Ritchie, R. H., Hamm, R. N., Ashley, J. C., Echenique, P. M., Gras-Marti, Alberto, editor, Urbassek, Herbert M., editor, Arista, Néstor R., editor, and Flores, Fernando, editor
- Published
- 1991
- Full Text
- View/download PDF
40. Correlation function and linear response function of homogeneous isotropic turbulence in the Eulerian and Lagrangian coordinates
- Author
-
Susumu Goto, Michio Otsuki, Takeshi Matsumoto, and Takeshi Ooshida
- Subjects
Direct numerical simulation ,FOS: Physical sciences ,turbulence simulation ,01 natural sciences ,010305 fluids & plasmas ,symbols.namesake ,Lagrangian and Eulerian specification of the flow field ,turbulence theory ,0103 physical sciences ,010306 general physics ,Condensed Matter - Statistical Mechanics ,Physics ,Homogeneous isotropic turbulence ,Statistical Mechanics (cond-mat.stat-mech) ,Mechanical Engineering ,Mathematical analysis ,Fluid Dynamics (physics.flu-dyn) ,Eulerian path ,Physics - Fluid Dynamics ,Statistical mechanics ,Condensed Matter Physics ,Linear response function ,Correlation function (statistical mechanics) ,Fourier transform ,Mechanics of Materials ,symbols - Abstract
We study the correlation function and mean linear response function of the velocity Fourier mode of statistically steady-state, homogeneous and isotropic turbulence in the Eulerian and Lagrangian coordinates through direct numerical simulation (DNS). As the Lagrangian velocity, we here adopt Kraichnan's Lagrangian history framework where Lagrangian particles are labelled with current positions and their velocity are measured at some time before. This Lagrangian velocity is numerically calculated with a method known as passive vector method. Our first goal is to study relation between the correlation function and the mean linear response function in the Eulerian and Lagrangian coordinates. Such a relation is known to be important in analysing the closed set of equations for the two functions, which are obtained by direct-interaction-approximation type closures. We demonstrate numerically that the fluctuation-dissipation theorem (proportionality between the two functions) does not hold. The relation is further investigated with general analytical expressions of the mean linear response function under stochastic settings, which are known as the fluctuation-response relations in non-equilibrium statistical mechanics. Our second goal is to identify characteristic times associated with the two functions and to compare the times between the Eulerian and Lagrangian coordinates. Our DNS result supports the common view that the Eulerian characteristic times have the sweeping-time scaling ($\propto k^{-1}$, where $k$ is the wavenumber) for both functions and the Lagrangian characteristic times in the inertial range have the Kolmogorov-time scaling ($\propto k^{-2/3}$) for both functions., Comment: 47 pages, 14 figures, published version. One typo in Eq.(2.2) is corrected
- Published
- 2021
41. Excited states in the adiabatic connection fluctuation-dissipation theory: Recovering missing correlation energy from the negative part of the density response spectrum
- Author
-
Daria Drwal, Ewa Pastorczak, and Katarzyna Pernal
- Subjects
Physics ,Quantum mechanics ,Excited state ,General Physics and Astronomy ,Function (mathematics) ,Physical and Theoretical Chemistry ,Dissipation ,Perturbation theory ,Adiabatic process ,Linear response function ,Wave function ,Random phase approximation - Abstract
The adiabatic connection (AC) theory offers an alternative to the perturbation theory methods for computing correlation energy in the multireference wavefunction framework. We show that the AC correlation energy formula can be expressed in terms of the density linear response function as a sum of components related to positive and negative parts of the transition energy spectrum. Consequently, generalization of the adiabatic connection fluctuation-dissipation theory to electronically excited states is obtained. The component of the linear response function related to the negative-transition energy enters the correlation energy expression with an opposite sign to that of the positive-transition part and is non-negligible in the description of excited states. To illustrate this, we analyze the approximate AC model in which the linear response function is obtained in the extended random phase approximation (ERPA). We demonstrate that AC can be successfully combined with the ERPA for excited states, provided that the negative-excitation component of the response function is rigorously accounted for. The resulting AC0D model, an extension of the AC0 scheme introduced in our earlier works, is applied to a benchmark set of singlet excitation energies of organic molecules. AC0D constitutes a significant improvement over AC0 by bringing the excitation energies of the lowest excited states to a satisfactory agreement with theoretical best estimates, which parallels or even exceeds the accuracy of the n-electron valence state perturbation theory method. For higher excitations, AC0D is less reliable due to the gradual deterioration of the underlying ERPA linear response.
- Published
- 2021
42. A Snapshot Review -- Fluctuations in Quantum Materials: From Skyrmions to Superconductivity
- Author
-
Joshua J. Turner, L. Shen, Matthew Seaberg, and E. Blackburn
- Subjects
Condensed Matter - Materials Science ,Strongly Correlated Electrons (cond-mat.str-el) ,Computer science ,Mechanical Engineering ,Physics beyond the Standard Model ,Skyrmion ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,02 engineering and technology ,Work in process ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Linear response function ,01 natural sciences ,Characterization (materials science) ,Theoretical physics ,Condensed Matter - Strongly Correlated Electrons ,Perspective (geometry) ,Mechanics of Materials ,Phase space ,0103 physical sciences ,General Materials Science ,010306 general physics ,0210 nano-technology ,Quantum - Abstract
Abstract By measuring a linear response function directly, such as the dynamic susceptibility, one can understand fundamental material properties. However, a fresh perspective can be offered by studying fluctuations. This can be related back to the dynamic susceptibility through the fluctuation–dissipation theorem, which relates the fluctuations in a system to its response, an alternate route to access the physics of a material. Here, we describe a new X-ray tool for material characterization that will offer an opportunity to uncover new physics in quantum materials using this theorem. We provide details of the method and discuss the requisite analysis techniques in order to capitalize on the potential to explore an uncharted region of phase space. This is followed by recent results on a topological chiral magnet, together with a discussion of current work in progress. We provide a perspective on future measurements planned for work in unconventional superconductivity. Graphical abstract We describe a new X-ray tool for material characterization that will offer an opportunity to uncover new physics in quantum materials using coherent, short-pulsed X-rays. We provide details of the method and discuss the requisite analysis techniques in order to capitalize on the potential to explore an uncharted region of phase space. This is followed by recent results on a topological chiral magnet, together with a discussion of current work in progress. We provide a perspective on future measurements planned for work in unconventional superconductivity.
- Published
- 2021
43. Linear response function of the Mayer bond order: an indicator to describe intrinsic chemical reactivity of molecules.
- Author
-
Yamanaka, Shusuke, Mitsuta, Yuki, Okumura, Mitsutaka, Yamaguchi, Kizashi, and Nakamura, Haruki
- Subjects
- *
REACTIVITY (Chemistry) , *BENZOIC acid , *SUBSTITUTION reactions , *NUMERICAL calculations , *DISSOCIATION (Chemistry) - Abstract
We here formulate and implement linear response function (LRF) of the Mayer bond order (MBO), which is expected to be a new indicator to describe intrinsic chemical reactivity of molecules. We calculate LRFs of the MBOs of para-substituted benzoic acids, and compare the results with the Hammett substituent constants and computational results of acid dissociation constants that were previously reported. The results are discussed from the viewpoint of the applicability of LRF of the MBO to estimate the relative reactivity of the substituted benzoic acids. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
44. The Second-Order-Polarization-Propagator Approximation SOPPA in a Four Component Spinor Basis
- Author
-
Schnack-Petersen, Anna Kristina, Simmermacher, Mats, Fasshauer, Elke, Jensen, Hans Jørgen Aagaard, Sauer, Stephan P. A., Schnack-Petersen, Anna Kristina, Simmermacher, Mats, Fasshauer, Elke, Jensen, Hans Jørgen Aagaard, and Sauer, Stephan P. A.
- Abstract
A theoretical framework for understanding molecular structures is crucial for the development of new technologies such as catalysts or solar cells. Apart from electronic excitations energies however, only spectroscopic properties of molecules consisting of lighter elements can be computationally described at high level of theory today, since heavy elements require a relativistic framework and most methods have only been derived in a non-relativistic one so far. Important new technologies like the above mentioned require molecules that contain heavier elements and hence there is a great need for the development of relativistic computational methods at higher level of accuracy. Here, the Second-Order-Polarization-Propagator-Approximation (SOPPA), which has proven very successful in the non-relativistic case, is adapted to a relativistic framework. The equations for SOPPA are presented in their most general form, i.e., in a non-canonical spin-orbital basis, which can be reduced to the canonical case, and the expressions needed for a relativistic four-component SOPPA are obtained. The equations are one-index transformed, giving more compact expressions that correspond to those already available for the four-component RPA. The equations are ready for implementation in a four-component quantum chemistry program, which will allow both linear response properties and excitation energies to be calculated relativistically at the SOPPA level.
- Published
- 2020
45. Eddy Length Scale Response to Static Stability Change in an Idealized Dry Atmosphere: A Linear Response Function Approach
- Author
-
Pedram Hassanzadeh, Zhiming Kuang, and Pak Wah Chan
- Subjects
Atmosphere ,Length scale ,Atmospheric Science ,Materials science ,Eddy ,Longitudinal static stability ,Mechanics ,Linear response function - Abstract
The response of mid-latitude equilibrated eddy length scale to static stability has long been questioned but not investigated in well-controlled experiments with unchanged mean zonal wind and meridional temperature gradient. With iterative use of the linear response function of an idealized dry atmosphere, we obtain a time-invariant and zonally-uniform forcing to decrease the near-surface temperature by over 2 K while keeping the change in zonal wind negligible (within 0.2m s−1). In such experiments of increased static stability, energy-containing zonal scale decreases by 3–4%, which matches with Rhines scale decrease near the jet core. Changes in Rossby radius (+2%), maximum baroclinic growth scale (-1%) and Kuo scale (0%) fail to match this change in zonal scale. These findings and well-controlled experiments help with better understanding of eddy–mean flow interactions and hence the mid-latitude circulation and its response to climate change.
- Published
- 2021
46. Efficient Time-Domain Approach for Linear Response Functions
- Author
-
Frank Ortmann and Michel Panhans
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics ,Quantum dynamics ,Time evolution ,General Physics and Astronomy ,FOS: Physical sciences ,State (functional analysis) ,Linear response function ,01 natural sciences ,Displacement (vector) ,Kubo formula ,Tensor (intrinsic definition) ,0103 physical sciences ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Time domain ,Statistical physics ,010306 general physics ,Mathematics - Abstract
We derive the general Kubo formula in a form that solely utilizes the time evolution of displacement operators. The derivation is based on the decomposition of the linear response function into its time symmetric and time anti-symmetric part. We relate this form to the well-known fluctuation-dissipation formula and discuss theoretical and numerical aspects of it. The approach is illustrated with an analytical example for magnetic resonance as well as a numerical example where we analyze the electrical conductivity tensor and the Chern insulating state of the disordered Haldane model. We introduce a highly efficient time-domain approach that describes the quantum dynamics of the resistivity of this model with an at least 1000-fold better performance in comparison to existing time-evolution schemes.
- Published
- 2021
- Full Text
- View/download PDF
47. Theoretical Investigation on Nearsightedness of Finite Model and Molecular Systems Based on Linear Response Function Analysis.
- Author
-
Mitsuta, Yuki, Yamanaka, Shusuke, Yamaguchi, Kizashi, Okumura, Mitsutaka, and Nakamura, Haruki
- Subjects
- *
MYOPIA , *FINITE model theory , *INFINITE square well , *ELECTRONS , *POLYPEPTIDES - Abstract
We examined nearsightedness of electronic matter (NEM) of finite systems on the basis of linear response function (LRF). From the computational results of a square-well model system, the behavior of responses obviously depends on the number of electrons (N): as N increases, LRF, δρ(r)/δv(r′), decays rapidly for the distance, ∣r−r′∣. This exemplifies that the principle suggested by Kohn and Prodan holds even for finite systems: the cause of NEM is destructive interference among electron density amplitudes. In addition, we examined double-well model systems, which have low-lying degenerate levels. In this case, there are two types of LRF: the cases of the half-filled and of full-filled in low-lying degenerate levels. The response for the former is delocalized, while that of the later is localized. These behaviors of model systems are discussed in relation to the molecular systems’ counterparts, H2, He22+, and He2 systems. We also see that NEM holds for the dissociated limit of H2, of which the mechanism is similar to that of the insulating state of solids as suggested by Kohn. We also examined LRF of alanine tripeptide system as well as butane and butadiene molecules, showing that NEM of the polypeptide system is caused by sp3 junctions at Cα atoms that prevent propagation of amplitudes of LRF, which is critically different from that of NEM for finite and infinite homogeneous systems. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
48. Microscopic insights into the protein-stabilizing effect of trimethylamine N-oxide (TMAO).
- Author
-
Jianqiang Ma, Pazos, Ileana M., and Feng Gai
- Subjects
- *
TRIMETHYLAMINE oxide , *HYDROGEN bonding , *PROTEIN folding , *AMINO acids , *PEPTIDES , *COMPUTATIONAL statistics - Abstract
Although it is widely known that trimethylamine N-oxide (TMAO), an osmolyte used by nature, stabilizes the folded state of proteins, the underlying mechanism of action is not entirely understood. To gain further insight into this important biological phenomenon, we use the C≡N stretching vibration of an unnatural amino acid, p-cyano-phenylalanine, to directly probe how TMAO affects the hydration and conformational dynamics of a model peptide and a small protein. By assessing how the lineshape and spectral diffusion properties of this vibration change with cosolvent conditions, we are able to show that TMAO achieves its protein-stabilizing ability through the combination of (at least) two mechanisms: (i) It decreases the hydrogen bonding ability of water and hence the stability of the unfolded state, and (ii) it acts as amolecular crowder, as suggested by a recent computational study, that can increase the stability of the folded state via the excluded volume effect. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
49. A Review Of The Linear Response Function In Condensed Matter Physics And Their Application In Some Elementary Processes
- Author
-
Kamsul Abraha, Ibnu Jihad, and Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada
- Subjects
Physics ,Quantization (physics) ,Classical mechanics ,Dispersion relation ,linear response theory ,response function ,general susceptibility ,magnetic susceptibility ,electric conductivity tensor ,Heisenberg ferromagnet ,Condensed Matter::Strongly Correlated Electrons ,Tensor ,Function (mathematics) ,theoritical physics, condensed matter ,Linear response function ,Quantum ,Magnetic susceptibility ,Magnetic field - Abstract
Linear response theory in quantum theory with its linear response function and its quantization process has been formulated. The relation between the linear response function with its generalized susceptibility, its symmetry properties, and its analyticity has been studied. These properties produce the dispersion relation or Kramers-Kronig relation. The explicit form of the quantum response function and generalized susceptibility also been reviewed. Applications of linear response functions have been described for three elementary processes. The process discussed is the magnetic field disturbance in the magnetic system that generates magnetic susceptibility, and the electric field disturbance in the electrical system that generates electrical conductivity tensor and the ferromagnet Heisenberg that generates its generalized susceptibility.
- Published
- 2020
50. Macroturbulence Response to Vertical Stratification Change Using Linear Response Function of an Idealized Dry Atmosphere
- Author
-
Zhiming Kuang, Pedram Hassanzadeh, and Pak Wah Chan
- Subjects
Physics::Fluid Dynamics ,Stratification (water) ,Environmental science ,Linear response function ,Atmospheric sciences ,Physics::Atmospheric and Oceanic Physics - Abstract
Rossby radius and Rhines scale are two popular scaling arguments for eddy length scale. They have not been tested in a well-controlled experiment with increased vertical stratification and unchanged jet. This is done using the linear response function of an idealized dry atmosphere calculated by Hassanzadeh and Kuang (2016). The resulting change in zonal wind is mostly less than 0.2m/s when temperature near surface is cooled by more than 2K. In such experiment, energy-containing zonal scale decreases, which is against the prediction of Rossby radius but consistent with the prediction of Rhines scale. Eddy kinetic energy decreases for all wavenumbers and latitudes, but eddy momentum flux strengthens locally around zonal wavenumber 8 and 40°S. This local strengthening is associated with a stronger Pearson correlation between u and v.
- Published
- 2020
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.