70 results on '"Yuki Kurashige"'
Search Results
2. Polarizing agents beyond pentacene for efficient triplet dynamic nuclear polarization in glass matrices.
- Author
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Keita Sakamoto, Tomoyuki Hamachi, Katsuki Miyokawa, Kenichiro Tateishi, Tomohiro Uesaka, Yuki Kurashige, and Nobuhiro Yanai
- Subjects
POLARIZATION (Nuclear physics) ,PENTACENE ,ELECTRON paramagnetic resonance ,ELECTRON distribution ,SPIN polarization - Abstract
Triplet dynamic nuclear polarization (triplet-DNP) is a technique that can obtain high nuclear polarization under moderate conditions. However, in order to obtain practically useful polarization, large single crystals doped with a polarizing agent must be strictly oriented with respect to the magnetic field to sharpen the electron spin resonance (ESR) spectra, which is a fatal problem that prevents its application to truly useful biomolecular targets. Instead of this conventional physical approach of controlling crystal orientation, here, we propose a chemical approach, i.e., molecular design of polarizing agents; pentacene molecules, the most typical triplet-DNP polarizing agent, are modified so as to make the triplet electron distribution wider and more isotropic without loss of the triplet polarization. The thiophene-modified pentacene exhibits a sharper and stronger ESR spectrum than the parent pentacene, and state-of-the-art quantum chemical calculations revealed that the direction of the spin polarization is altered by the modification with thiophene moieties and the size of D and E parameters are reduced from parent pentacene due to the partial delocalization of spin densities on the thiophene moieties. The triplet-DNP with the new polarizing agent successfully exceeds the previous highest ¹H polarization of glassy materials by a factor of 5. This demonstrates the feasibility of a polarizing agent that can surpass pentacene, the best polarizing agent for more than 30 y since triplet-DNP was first reported, in the unoriented state. This work provides a pathway toward practically useful high nuclear polarization of various biomolecules by triplet-DNP. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
3. Sunscreen redox status in a multicellular cyanobacterium visualized by Raman scattering spectral microscope
- Author
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Kouto Tamamizu, Toshio Sakamoto, Yuki Kurashige, Shuho Nozue, and Shigeichi Kumazaki
- Abstract
UV radiation, desiccation, and starvation induce some cyanobacteria to produce a UVA-absorbing pigment, scytonemin, at extracellular sheaths. Although the accumulation of scytonemin is recognizable as dark sheaths through optical microscopes, it has been nontrivial to identify its redox status and obtain its subcellular distribution in response to physiological conditions. Here, we show that a spontaneous Raman scattering spectral microscopy based on an excitation-laser-line-scanning method unveil 3D subcellular distributions of non-UV-induced scytonemins with distinct redox statuses in a filamentous cyanobacterium with a single nitrogen-fixing cell at the basal end. Cellular differentiations and scytonemin redox conditions were simultaneously visualized with an excitation wavelength at 1064 nm that is virtually free from the optical screening by the dark sheaths. The molecular imaging results give insights into not only secretion mechanisms of the sunscreen pigment but also interdependence between photosynthesis, nitrogen fixation, and redox homeostasis in one of the simplest forms of multicellular organisms.
- Published
- 2022
4. Scytonemin redox status in a filamentous cyanobacterium visualized by an excitation-laser-line-scanning spontaneous Raman scattering spectral microscope
- Author
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Kouto, Tamamizu, Toshio, Sakamoto, Yuki, Kurashige, Shuho, Nozue, and Shigeichi, Kumazaki
- Subjects
Instrumentation ,Spectroscopy ,Atomic and Molecular Physics, and Optics ,Analytical Chemistry - Abstract
Some cyanobacteria produce a UVA-absorbing pigment, scytonemin, at extracellular sheaths. Although scytonemin-containing dark sheaths are recognizable through optical microscopes and its redox changes have been known for decades, there has been no report to obtain images of both oxidized and reduced scytonemins at subcellular resolution. Here, we show that a spontaneous Raman scattering spectral microscopy based on an excitation-laser-line-scanning method unveil 3D subcellular distributions of both the oxidized and reduced scytonemins in a filamentous cyanobacterium. The redox changes of scytonemin were supported by comparison in the Raman spectra between the cyanobacterial cells, solid-state scytonemin and quantum chemical normal mode analysis. Distributions of carotenoids, phycobilins, and the two redox forms of scytonemin were simultaneously visualized with an excitation wavelength at 1064 nm that is virtually free from the optical screening by the dark sheaths. The redox differentiation of scytonemin will advance our understanding of the redox homeostasis and secretion mechanisms of individual cyanobacteria as well as microscopic chemical environments in various microbial communities. The line-scanning Raman microscopy based on the 1064 nm excitation is thus a promising tool for exploring hitherto unreported Raman spectral features and distribution of nonfluorescent molecules embedded below nontransparent layers for visible light, while avoiding interference by autofluorescence.
- Published
- 2023
5. Matrix Product State Formulation of the MCTDH Theory in Local Mode Representations for Anharmonic Potentials
- Author
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Kentaro Hino and Yuki Kurashige
- Subjects
Physical and Theoretical Chemistry ,Computer Science Applications - Abstract
The matrix product state formulation of the multiconfiguration time-dependent Hartree theory, MPS-MCTDH, reported previously [Kurashige
- Published
- 2022
6. Jastrow-type Decomposition in Quantum Chemistry for Low-Depth Quantum Circuits
- Author
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Yuta Matsuzawa and Yuki Kurashige
- Subjects
Chemical Physics (physics.chem-ph) ,Physics ,Quantum Physics ,010304 chemical physics ,FOS: Physical sciences ,01 natural sciences ,Computer Science Applications ,symbols.namesake ,Quantum circuit ,Operator (computer programming) ,Pauli exclusion principle ,Coupled cluster ,Particle number operator ,Physics - Chemical Physics ,0103 physical sciences ,symbols ,Physical and Theoretical Chemistry ,Quantum Physics (quant-ph) ,Quantum ,Mathematical physics ,Quantum computer ,Ansatz - Abstract
We propose an efficient ${\cal O}(N^2)$-parameter ansatz that consists of a sequence of exponential operators, each of which is a unitary variant of Neuscamman's cluster Jastrow operator. The ansatz can also be derived as a decomposition of T$_2$ amplitudes of the unitary coupled cluster with generalized singles and doubles, which gives a near full-CI energy, and reproduces it by extending the exponential operator sequence. Because the cluster Jastrow operators are expressed by a product of number operators and the derived Pauli operator products, namely the Jordan-Wigner strings, are all commutative, it does not require the Trotter approximation to implement to a quantum circuit and should be a good candidate for the variational quantum eigensolver algorithm by a near-term quantum computer. The accuracy of the ansatz was examined for dissociation of a nitrogen dimer, and compared with other existing ${\cal O}(N^2)$-parameter ansatzs. Not only the original ansatzs defined in the second-quantization form but also their Trotterized variants, in which the cluster amplitudes are optimized to minimize the energy obtained with a few, typically single, Trotter steps, were examined by quantum circuit simulators., Comment: 9 pages, 3 figures
- Published
- 2020
7. Soft chromophore featured liquid porphyrins and their utilization toward liquid electret applications
- Author
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Nagao Kobayashi, Kouji Suemori, Manabu Yoshida, Yuki Kurashige, Osamu Yamamuro, Izuru Kawamura, Hiroaki Isago, Tomohisa Takaya, Shinsuke Ishihara, Takashi Nakanishi, Kazuhiko Nagura, Yasuhisa Mizutani, Akinori Saeki, Avijit Ghosh, Masami Nirei, and Koichi Iwata
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Materials science ,Science ,Stretchable electronics ,General Physics and Astronomy ,Nanotechnology ,02 engineering and technology ,Viscous liquid ,010402 general chemistry ,01 natural sciences ,Article ,General Biochemistry, Genetics and Molecular Biology ,chemistry.chemical_compound ,Fluidics ,lcsh:Science ,Alkyl ,chemistry.chemical_classification ,Fluids ,Multidisciplinary ,Self-assembly ,General Chemistry ,Organic molecules in materials science ,Chromophore ,021001 nanoscience & nanotechnology ,Porphyrin ,Piezoelectricity ,0104 chemical sciences ,chemistry ,lcsh:Q ,Electret ,Devices for energy harvesting ,0210 nano-technology - Abstract
Optoelectronically active viscous liquids are ideal for fabricating foldable/stretchable electronics owing to their excellent deformability and predictable π-unit–based optoelectronic functions, which are independent of the device shape and geometry. Here we show, unprecedented ‘liquid electret’ devices that exhibit mechanoelectrical and electroacoustic functions, as well as stretchability, have been prepared using solvent-free liquid porphyrins. The fluidic nature of the free-base alkylated-tetraphenylporphyrins was controlled by attaching flexible and bulky branched alkyl chains at different positions. Furthermore, a subtle porphyrin ring distortion that originated from the bulkiness of alkyl chains was observed. Its consequences on the electronic perturbation of the porphyrin-unit were precisely elucidated by spectroscopic techniques and theoretical modelling. This molecular design allows shielding of the porphyrin unit by insulating alkyl chains, which facilitates its corona-charged state for a long period under ambient conditions., Though electret materials are attractive for realizing flexible mechanoelectrical devices, these materials are typically solid films. Here, the authors report stretchable ‘liquid-electret’ devices consisting solvent-free liquid porphyrins that show piezoelectric and electroacoustic functionality.
- Published
- 2019
8. Molecular Technology of Excited Triplet State
- Author
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Yong-Jin Pu, So Kawata, Yuki Kurashige, and Nobuhiro Yanai
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Materials science ,Near infrared light ,Photovoltaics ,business.industry ,Excited state ,Triplet state ,Atomic physics ,business ,Photon upconversion - Published
- 2019
9. Electronically Excited Solute Described by RISM Approach Coupled with Multireference Perturbation Theory: Vertical Excitation Energies of Bioimaging Probes
- Author
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Takeshi Yanai, Daisuke Yokogawa, Yuki Kurashige, and Ryosuke Shimizu
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Infrared Rays ,Electronic structure ,Molecular Dynamics Simulation ,010402 general chemistry ,01 natural sciences ,Molecular physics ,Fluorescence ,Spectral line ,0103 physical sciences ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Perturbation theory ,Fluorescent Dyes ,Physics ,Molecular Structure ,010304 chemical physics ,Density matrix renormalization group ,Solvation ,Statistical mechanics ,Photochemical Processes ,0104 chemical sciences ,Computer Science Applications ,Solubility ,Excited state ,Solvents ,Quantum Theory ,Excitation - Abstract
For theoretically studying molecules with fluorescence in the near-infrared region, high-accuracy determination of state energy level is required for meaningful analyses since the spectra of interest are of very narrow energy range. In particular, these molecules are in many cases handled in solution; therefore, consideration of the solvation effect is essential upon calculation together with the electronic structure of the excited state. Earlier studies showed that they cannot be described with conventional methods such as PCM-TD-DFT, yielding results far from experimental data. Here, we have developed a new method by combining a solvation theory based on statistical mechanics (RISM) and a multireference perturbation theory (CASPT2) with the extension of the density matrix renormalization group reference states for calculating the photochemical properties of near-infrared molecules and have obtained higher-accuracy prediction.
- Published
- 2018
10. Importance of dynamical electron correlation in diabatic couplings of electron-exchange processes
- Author
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Soichiro Nishio and Yuki Kurashige
- Subjects
General Physics and Astronomy ,Physical and Theoretical Chemistry - Abstract
We demonstrate the importance of the dynamical electron correlation effect in diabatic couplings of electron-exchange processes in molecular aggregates. To perform a multireference perturbation theory with large active space of molecular aggregates, an efficient low-rank approximation is applied to the complete active space self-consistent field reference functions. It is known that kinetic rates of electron-exchange processes, such as singlet fission, triplet–triplet annihilation, and triplet exciton transfer, are not sufficiently explained by the direct term of the diabatic couplings but efficiently mediated by the low-lying charge transfer states if the two molecules are in close proximity. It is presented in this paper, however, that regardless of the distance of the molecules, the direct term is considerably underestimated by up to three orders of magnitude without the dynamical electron correlation, i.e., the diabatic states expressed in the active space are not adequate to quantitatively reproduce the electron-exchange processes.
- Published
- 2022
11. Phosphorescence Resulting from Interaction between Two Non-equivalent Metals on a Helical π-Conjugated Surface
- Author
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Midori Akiyama, Miki Hasegawa, Ayumi Ishii, Kyoko Nozaki, Yuto Tsuchiya, and Yuki Kurashige
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010405 organic chemistry ,Ligand ,Organic Chemistry ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,Ring (chemistry) ,01 natural sciences ,Biochemistry ,0104 chemical sciences ,Ruthenium ,chemistry.chemical_compound ,Crystallography ,chemistry ,Helicene ,Cyclopentadienyl complex ,Ruthenocene ,Butyronitrile ,Phosphorescence - Abstract
A [7]helicene bis-ruthenium complex, with one ruthenium atom bound to the cyclopentadienyl (Cp) ring and the other coordinated to the arene ring at the edge of the helicene, was synthesized. This complex showed phosphorescence both in butyronitrile (Φ=31 %, 77 K) and in the solid state (Φ=18 %, 77 K). The two non-equivalent ruthenium metal atoms, attached to the helicene ligand, interact with each other upon photoabsorption and emission.
- Published
- 2018
12. Influence of the choice of projection manifolds in the CASPT2 implementation
- Author
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Takeshi Yanai, Jakub Chalupský, Per-Åke Malmqvist, Roland Lindh, Masaaki Saitow, and Yuki Kurashige
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Source code ,010304 chemical physics ,Degree (graph theory) ,Computer science ,media_common.quotation_subject ,Suite ,Biophysics ,Electronic structure ,010402 general chemistry ,Condensed Matter Physics ,01 natural sciences ,Projection (linear algebra) ,0104 chemical sciences ,0103 physical sciences ,Code (cryptography) ,Perturbation theory (quantum mechanics) ,Complete active space ,Physical and Theoretical Chemistry ,Molecular Biology ,Algorithm ,media_common - Abstract
The Complete Active Space Second-Order Perturbation Theory (CASPT2) is well-established as a high-accuracy electronic structure method. It was originally implemented in the early 1990s to an efficient computer code in the molcas program suite, and this implementation has been extensively used as a standard tool. Here, we report a comparison of it against two independent computer-aided implementations of the CASPT2 method, revealing that the CASPT2 energies provided by the original code of molcas (version 8 or earlier) are inconsistent with the predictions of the lately developed computer-aided implementations. It is shown that this error is associated with the projections of the first-order equation onto the fully internally contracted multireference bases which are partially inconsistent between the left- and right-hand sides. The degree of the errors is assessed by performing illustrative CASPT2 calculations. The errors in total CASPT2 energies are demonstrated to be negligible relative to chemical accuracy in many cases, while there is a difficult case where they may substantially alter chemical description. The incorporation of the consistent projections into molcas has been carried out, which is available in the version 8 sp1. (Less)
- Published
- 2016
13. Rank-one basis made from matrix-product states for a low-rank approximation of molecular aggregates
- Author
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Yuki Kurashige and Soichiro Nishio
- Subjects
Physics ,010304 chemical physics ,Intermolecular force ,Diabatic ,General Physics and Astronomy ,Quantum entanglement ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,symbols.namesake ,Excited state ,Quantum mechanics ,0103 physical sciences ,symbols ,Complete active space ,Physical and Theoretical Chemistry ,Wave function ,Hamiltonian (quantum mechanics) ,Matrix product state - Abstract
An efficient low-rank approximation to complete active space (CAS) wavefunctions for molecular aggregates is presented. Molecular aggregates usually involve two different characteristic entanglement structures: strong intramolecular entanglement and weak intermolecular entanglement. In the method, low-lying electronic states of molecular aggregates are efficiently expanded by a small number of rank-one basis states that are direct products of monomolecular wavefunctions, each of which is written as a highly entangled state such as the matrix product state (MPS). The complexities raised by strong intramolecular entanglement are therefore encapsulated by the MPS and eliminated from the degree of freedom of the effective Hamiltonian of molecular aggregates. It is demonstrated that the excitation energies of low-lying excited states of a pair of bacteriochlorophyll units with CAS(52e, 50o) are accurately reproduced by only five rank-one basis states. Because the rank-one basis states naturally have diabatic character and reproduce the low-lying spectrum of the CAS space, off-diagonal elements of the Hamiltonian are expected to give accurate diabatic couplings. It is also demonstrated that the energy splitting and the diabatic couplings in anthracene dimer systems are improved by augmenting with additional rank-one basis states.
- Published
- 2019
14. A Mechanistic Insight into Metal-Cluster π-Envelopment: A Dual Binding Mode Involving Bent and Planar Ligand-Conformers
- Author
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Kohei Masai, Tetsuro Murahashi, Yuki Kurashige, Katsunori Shirato, and Koji Yamamoto
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010405 organic chemistry ,Chemistry ,Ligand ,Visible light irradiation ,Bent molecular geometry ,Metals and Alloys ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Metal ,chemistry.chemical_compound ,Crystallography ,Planar ,visual_art ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,Benzene ,Conformational isomerism ,Metal clusters - Abstract
Metal clusters are effectively stabilized by bridging π-coordination of planar π-conjugated unsaturated hydrocarbons. However, the mechanism of π-envelopment of a metal cluster has been elusive. By employing 1,2-bis(4-aryl-1,3-butadienyl)benzene as the π-conjugated ligand, we found that the π-envelopment of a Pd4 cluster proceeded in a stepwise manner, where the sp(2)-carbon ligands initially envelop the Pd4 cluster through a bent binding mode, and then isomerized to a thermodynamically more stable planar mode under mild heating or visible light irradiation. The involvement of a bent binding mode indicates the kinetically preferred coordination at the axial coordination site trans to a metal-metal bond.
- Published
- 2016
15. Complete active space second-order perturbation theory with cumulant approximation for extended active-space wavefunction from density matrix renormalization group.
- Author
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Yuki Kurashige, Jakub Chalupsky, Tran Nguyen Lan, and Takeshi Yanai
- Subjects
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WAVE functions , *QUANTUM perturbations , *APPROXIMATION theory , *DENSITY matrices , *RENORMALIZATION group , *MOLECULAR orbitals , *EXCITED states - Abstract
We report an extension of our previous development that incorporated quantum-chemical density ma-trix renormalization group (DMRG) into the complete active space second-order perturbation theory (CASPT2) [Y. Kurashige and T. Yanai, J. Chem. Phys. 135, 094104 (2011)]. In the previous study, the combined theory, referred to as DMRG-CASPT2, was built upon the use of pseudo-canonical molecular orbitals (PCMOs) for one-electron basis. Within the PCMO basis, the construction of the four-particle reduced density matrix (4-RDM) using DMRG can be greatly facilitated because of simplicity in the multiplication of 4-RDM and diagonal Fock matrix in the CASPT2 equation. In this work, we develop an approach to use more suited orbital basis in DMRG-CASPT2 calcu-lations, e.g., localized molecular orbitals, in order to extend the domain of applicability. Because the multiplication of 4-RDM and generalized Fock matrix is no longer simple in general orbitals, an approximation is made to it using the cumulant reconstruction neglecting higher-particle cumu-lants. Also, we present the details of the algorithm to compute 3-RDM of the DMRG wavefunction as an extension of the 2-RDM algorithm of Zgid et al. [J. Chem. Phys. 128, 144115 (2008)] and Chan et al. [J. Chem. Phys. 128, 144117 (2008)]. The performance of the extended DMRG-CASPT2 approach was examined for large-scale multireference systems, such as low-lying excited states of long-chain polyenes and isomerization potential of {[Cu(NH3)3]2O2}2+. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
16. Singlet Fission of Non-polycyclic Aromatic Molecules in Organic Photovoltaics
- Author
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Masaki Hada, Ayaka Saito, Hiroshi Katagiri, So Kawata, Teruo Beppu, Junji Kido, Yuki Kurashige, and Yong-Jin Pu
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Photocurrent ,Materials science ,Organic solar cell ,Mechanical Engineering ,Exciton ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Dissociation (chemistry) ,0104 chemical sciences ,Mechanics of Materials ,Singlet fission ,Physics::Atomic and Molecular Clusters ,Molecule ,Condensed Matter::Strongly Correlated Electrons ,General Materials Science ,Quantum efficiency ,Nuclear Experiment ,0210 nano-technology - Abstract
Singlet fission of thienoquinoid compounds in organic photovoltaics is demonstrated. The escalation of the thienoquinoid length of the compounds realizes a suitable packing structure and energy levels for singlet fission. The magnetic-field dependence of the photocurrent and the external quantum efficiency of the devices reveal singlet fission of the compounds and dissociation of triplet excitons into charges.
- Published
- 2015
17. Fully Internally Contracted Multireference Configuration Interaction Theory Using Density Matrix Renormalization Group: A Reduced-Scaling Implementation Derived by Computer-Aided Tensor Factorization
- Author
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Yuki Kurashige, Masaaki Saitow, and Takeshi Yanai
- Subjects
Tensor contraction ,Physics ,Factorization ,Electronic correlation ,Computational chemistry ,Density matrix renormalization group ,Quantum mechanics ,Multireference configuration interaction ,Physical and Theoretical Chemistry ,Symbolic computation ,Wave function ,Scaling ,Computer Science Applications - Abstract
We present an extended implementation of the multireference configuration interaction (MRCI) method combined with the quantum-chemical density matrix renormalization group (DMRG). In the previous study, we introduced the combined theory, referred to as DMRGMRCI, as a method to calculate high-level dynamic electron correlation on top of the DMRG wave function that accounts for active-space (or strong) correlation using a large number of active orbitals. The DMRG-MRCI method is built on the full internal-contraction scheme for the compact reference treatment and on the cumulant approximation for the treatment of the four-particle rank reduced density matrix (4-RDM). The previous implementation achieved the MRCI calculations with the active space (24e,24o), which are deemed the record largest, whereas the inherent Nact 8 × N complexity of computation was found a hindrance to using further large active space. In this study, an extended optimization of the tensor contractions is developed by explicitly incorporating the rank reduction of the decomposed form of the cumulant-approximated 4-RDM into the factorization. It reduces the computational scaling (to Nact7 × N) as well as the cache-miss penalty associated with direct evaluation of complex cumulant reconstruction. The present scheme, however, faces the increased complexity of factorization patterns for optimally implementing the tensor contraction terms involving the decomposed 4-RDM objects. We address this complexity using the enhanced symbolic manipulation computer program for deriving and coding programmable equations. The new DMRG-MRCI implementation is applied to the determination of the stability of the iron(IV)-oxo porphyrin relative to the iron(V) electronic isomer (electromer) using the active space (29e,29o) (including four second d-shell orbitals of iron) with triple-ζ-quality atomic orbital basis sets. The DMRG-cu(4)-MRCI+Q model is shown to favor the triradicaloid iron(IV)-oxo state as the lowest energy state and characterize the iron(V) electromer as thermally inaccessible, supporting the earlier experimental and density functional studies. This conflicts with the previous MR calculations using the restricted activespace second-order perturbation theory (RASPT2) with the similar-size active space (29e,28o) reported by Pierloot et al. (Radoń, M.; Broclawik, E.; Pierloot, K. J. Chem. Theory Comput. 2011, 7, 898), showing that the hypothetical iron(V) state indicated by recent laser flash photolysis (LFP) studies is likely thermally accessible because of its underestimated relative energy.
- Published
- 2015
18. Prediction models considering psychological factors to identify pain relief in conservative treatment of people with knee osteoarthritis: A multicenter, prospective cohort study
- Author
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Kenta Hirohama, Yuki Kurashige, Ryosuke Masuda, Tetsushi Morita, Seisuke Sato, Shinichi Yokota, Shintaro Miyamoto, Ryo Tanaka, and Kenichiro Mito
- Subjects
Male ,medicine.medical_specialty ,Osteoarthritis ,Conservative Treatment ,03 medical and health sciences ,Disability Evaluation ,0302 clinical medicine ,Musculoskeletal Pain ,Predictive Value of Tests ,Numeric Rating Scale ,Medicine ,Humans ,Pain Management ,Orthopedics and Sports Medicine ,Prospective Studies ,Prospective cohort study ,Physical Therapy Modalities ,Aged ,Pain Measurement ,030222 orthopedics ,Receiver operating characteristic ,business.industry ,Cognition ,Middle Aged ,Osteoarthritis, Knee ,medicine.disease ,Predictive value of tests ,Orthopedic surgery ,Physical therapy ,Surgery ,Pain catastrophizing ,Female ,business ,030217 neurology & neurosurgery - Abstract
Background Pain-related affective and/or cognitive characteristics such as depressive symptoms, pain catastrophizing, and self-efficacy are known to exacerbate pain in people with knee osteoarthritis. However, no studies have investigated whether these psychological factors can interfere with pain relief during conservative treatment. The object of this study was to assess the prediction models considering psychological factors to predict pain relief in people with knee osteoarthritis receiving conservative treatment. Methods Study design was a multicenter, and prospective cohort study. Data were collected in the department of physical therapy in 1 hospital and 7 orthopedic clinics. Eighty-eight people with knee osteoarthritis participated in this study and were followed for 3 months. The numeric rating scale and the Knee Injury and Osteoarthritis Outcome Score scale were used to evaluate pain relief. Potential predictors for pain relief were depressive symptoms, self-efficacy, and pain catastrophizing. The classification and regression trees methodology was used to develop the model for predicting the presence of pain relief at 1 and 3 months after the start of observation. The prediction accuracy was evaluated using the area under the receiver operating characteristic curves (AUCs). Results The model at 1 month after the start of observation included pain intensity at baseline, positive affect, and disease duration. The AUC of this model was 0.793 (95% confidential interval, 0.687–0.898). The model at 3 months after the start of observation included pain catastrophizing and self-efficacy. The AUC of this model was 0.808 (95% confidential interval, 0.682–0.934). Conclusions The accuracy of prediction model considering pain-related affective and/or cognitive characteristics is moderate for pain relief in people with knee osteoarthritis receiving conservative treatment.
- Published
- 2018
19. Three-Dimensional Sandwich Nanocubes Composed of 13-Atom Palladium Core and Hexakis-Carbocycle Shell
- Author
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Hiroshige Yamaura, Tetsuro Murahashi, Yuki Kurashige, Kosuke Iwata, Kenta Kurashima, Koshi Miyazawa, Koji Yamamoto, and Masahiro Teramoto
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010405 organic chemistry ,Chemistry ,Shell (structure) ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Crystallography ,Colloid and Surface Chemistry ,Octahedron ,Transition metal ,Agglomerate ,Atom ,Cluster (physics) ,Group 2 organometallic chemistry ,Palladium - Abstract
Coordination of cyclic unsaturated hydrocarbons to transition metal generally gives bis-ligated sandwich complexes, which are a fundamental class of organometallic compounds. This sandwich structure may be extended to a higher-order three-dimensional one when more than two carbocyclic ligands surround an agglomerate of many transition metal atoms. Here, we report synthesis of three-dimensional sandwich nanocube compounds containing a close-packed transition metal cluster core. Reduction of a [Pd3(μ3-C7H7)2]2+ with tetraarylborate under neat conditions afforded [Pd13(μ4-C7H7)6]2+ containing a cuboctahedral Pd13 core with an octahedral ligand-shell.
- Published
- 2018
20. Experimental and theoretical investigation of fluorescence solvatochromism of dialkoxyphenyl-pyrene molecules
- Author
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Koichi Iwata, Yuki Kurashige, Fengniu Lu, Tomohisa Takaya, Takashi Nakanishi, and Naoki Kitamura
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010405 organic chemistry ,Chemistry ,Solvatochromism ,General Physics and Astronomy ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Fluorescence ,0104 chemical sciences ,chemistry.chemical_compound ,Intramolecular force ,Excited state ,Phenyl group ,Molecule ,Pyrene ,Physical and Theoretical Chemistry ,HOMO/LUMO - Abstract
We investigated the fluorescence properties of dialkoxyphenyl-pyrene molecules experimentally as well as theoretically. Our experiments confirmed fluorescence solvatochromism in 2,5-dimethoxyphenyl-pyrene and, in contrast there was no significant solvent-effect on the emission properties of the isomers, 3,5- and 2,6-dimethoxyphenyl-pyrene. This clear difference in the solvent-dependence would reflect the difference in character of the excited-state between the isomers, which differ only in the substitution positions of the two methoxy groups. The positional effects of the di-substituted molecules are successfully explained theoretically by the topologies of the highest occupied molecular orbital of the phenyl group that are governed by the relative positions of the two substituents, though it is somewhat contradictory to the meta-effect for the mono-substituted molecules. Theoretical calculations were also used to analyze the character of the excited states; 2,5-dimethoxyphenyl-pyrene alone exhibited an intramolecular charge transfer character for the excited state, which was responsible for the solvatochromism effect. The dynamics of the excited states were analyzed using time-resolved fluorescence measurements, in which a characteristic increase of the fluorescence intensity was observed for 2,5-dialkoxyphenyl-pyrene; this observation was supported by the theoretical calculations as well.
- Published
- 2017
21. Synthesis of Molecular Wires Strapped by π-Conjugated Side Chains: Integration of Dehydrobenzo[20]annulene Units
- Author
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Masami Ohsawa, Yuki Kurashige, Yasushi Tsuji, Tetsuaki Fujihara, Hiroshi Masai, and Jun Terao
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Molecular wire ,Chemistry ,Stereochemistry ,Intramolecular force ,Organic Chemistry ,Polymer chemistry ,Side chain ,Annulene ,Conjugated system - Abstract
In this study, π-conjugated molecular wires strapped by cyclic π-conjugated side chains were efficiently synthesized by the integration of dehydrobenzo[20]annulene units by intramolecular Glaser-type cyclization under high dilution conditions.
- Published
- 2015
22. Aggregation-Induced Photon Upconversion through Control of the Triplet Energy Landscapes of the Solution and Solid States
- Author
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Yuki Kurashige, Pengfei Duan, Nobuo Kimizuka, and Nobuhiro Yanai
- Subjects
Annihilation ,Photoisomerization ,Chemistry ,Energy landscape ,General Medicine ,General Chemistry ,Photochemistry ,Molecular physics ,Catalysis ,Photon upconversion ,chemistry.chemical_compound ,Excited state ,Triplet state ,Ground state ,Derivative (chemistry) - Abstract
Aggregation-induced photon upconversion (iPUC) based on control of the triplet energy landscape is demonstrated for the first time. When a triplet state of a cyano-substituted 1,4-distyrylbenzene derivative is sensitized in solution, no upconverted emission based on triplet-triplet annihilation (TTA) was observed. In stark contrast, crystalline solids obtained by drying the solution revealed clear upconverted emission. Theoretical studies unveiled an underlying switching mechanism: the excited triplets in solution immediately decay back to the ground state through conformational twisting around a CC bond and photoisomerization, whereas this deactivation path is effectively inhibited in the solid state. The finding of iPUC phenomena highlights the importance of controlling excited energy landscapes in condensed molecular systems.
- Published
- 2015
23. Modulation of Benzene or Naphthalene Binding to Palladium Cluster Sites by the Backside-Ligand Effect
- Author
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Takeshi Yanai, Kohei Takase, Yuki Kurashige, Yuki Ishikawa, Koji Yamamoto, Seita Kimura, and Tetsuro Murahashi
- Subjects
Chemistry ,Ligand ,chemistry.chemical_element ,General Medicine ,General Chemistry ,Photochemistry ,Catalysis ,Metal ,chemistry.chemical_compound ,Cyclooctatetraene ,visual_art ,visual_art.visual_art_medium ,Cluster (physics) ,Reactivity (chemistry) ,Benzene ,Palladium ,Naphthalene - Abstract
The backside-ligand modulation strategy to enhance the substrate binding property of Pd clusters is reported. The benzene or naphthalene binding ability of Pd3 or Pd4 clusters is enhanced significantly by the backside cyclooctatetraene ligand, leading to the formation of the first solution-stable benzene- or naphthalene Pd clusters. The present results imply that the ligand design of the metal clusters, especially for the backside ligand of the metal cluster site, is crucial to acquire a desired reactivity of metal clusters.
- Published
- 2015
24. Acid/base-regulated reversible electron transfer disproportionation of N–N linked bicarbazole and biacridine derivatives
- Author
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Masaki Kawano, Go Nakamura, Palash Pandit, Koji Yamamoto, Yumi Yakiyama, Shuhei Higashibayashi, Toshikazu Nakamura, Katsuyuki Nishimura, Takeshi Yanai, Shigeyuki Masaoka, Yuki Kurashige, and Ko Furukawa
- Subjects
chemistry.chemical_classification ,Electron transfer ,chemistry ,Reagent ,Disproportionation ,General Chemistry ,Electron acceptor ,Proton-coupled electron transfer ,Photochemistry ,Redox ,Chemical synthesis ,Bond cleavage - Abstract
Regulation of electron transfer on organic substances by external stimuli is a fundamental issue in science and technology, which affects organic materials, chemical synthesis, and biological metabolism. Nevertheless, acid/base-responsive organic materials that exhibit reversible electron transfer have not been well studied and developed, owing to the difficulty in inventing a mechanism to associate acid/base stimuli and electron transfer. We discovered a new phenomenon in which N–N linked bicarbazole (BC) and tetramethylbiacridine (TBA) derivatives undergo electron transfer disproportionation by acid stimulus, forming their stable radical cations and reduced species. The reaction occurs through a biradical intermediate generated by the acid-triggered N–N bond cleavage reaction of BC or TBA, which acts as a two electron acceptor to undergo electron transfer reactions with two equivalents of BC or TBA. In addition, in the case of TBA the disproportionation reaction is highly reversible through neutralization with NEt3, which recovers TBA through back electron transfer and N–N bond formation reactions. This highly reversible electron transfer reaction is possible due to the association between the acid stimulus and electron transfer via the acid-regulated N–N bond cleavage/formation reactions which provide an efficient switching mechanism, the ability of the organic molecules to act as multi-electron donors and acceptors, the extraordinary stability of the radical species, the highly selective reactivity, and the balance of the redox potentials. This discovery provides new design concepts for acid/base-regulated organic electron transfer systems, chemical reagents, or organic materials.
- Published
- 2015
25. Scalar Relativistic Calculations of Hyperfine Coupling Constants Using Ab Initio Density Matrix Renormalization Group Method in Combination with Third-Order Douglas–Kroll–Hess Transformation: Case Studies on 4d Transition Metals
- Author
-
Yuki Kurashige, Tran Nguyen Lan, and Takeshi Yanai
- Subjects
Electronic correlation ,Atomic orbital ,Chemistry ,Density matrix renormalization group ,Quantum mechanics ,Atom ,Scalar (mathematics) ,Isotropy ,Ab initio ,Complete active space ,Physical and Theoretical Chemistry ,Computer Science Applications - Abstract
We have developed a new computational scheme for high-accuracy prediction of the isotropic hyperfine coupling constant (HFCC) of heavy molecules, accounting for the high-level electron correlation effects, as well as the scalar-relativistic effects. For electron correlation, we employed the ab initio density matrix renormalization group (DMRG) method in conjunction with a complete active space model. The orbital-optimization procedure was employed to obtain the optimized orbitals required for accurately determining the isotropic HFCC. For the scalar-relativistic effects, we initially derived and implemented the Douglas-Kroll-Hess (DKH) hyperfine coupling operators up to the third order (DKH3) by using the direct transformation scheme. A set of 4d transition-metal radicals consisting of Ag atom, PdH, and RhH2 were chosen as test cases. Good agreement between the isotropic HFCC values obtained from DMRG/DKH3 and experiment was archived. Because there are no available gas-phase values for PdH and RhH2 radicals in the literature, the results from the present high-level theory may serve as benchmark data.
- Published
- 2014
26. Reactivity of the Binuclear Non-Heme Iron Active Site of Δ9 Desaturase Studied by Large-Scale Multireference Ab Initio Calculations
- Author
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Lubomír Rulíšek, Edward I. Solomon, Takeshi Yanai, Yuki Kurashige, Jakub Chalupský, Martin Srnec, and Tibor András Rokob
- Subjects
chemistry.chemical_classification ,Double bond ,biology ,Chemistry ,Reaction step ,Active site ,Protonation ,General Chemistry ,Biochemistry ,Heterolysis ,Catalysis ,Colloid and Surface Chemistry ,Catalytic cycle ,Ab initio quantum chemistry methods ,Computational chemistry ,biology.protein ,Complete active space - Abstract
The results of density matrix renormalization group complete active space self-consistent field (DMRG-CASSCF) and second-order perturbation theory (DMRG-CASPT2) calculations are presented on various structural alternatives for the O-O and first C-H activating step of the catalytic cycle of the binuclear nonheme iron enzyme Δ(9) desaturase. This enzyme is capable of inserting a double bond into an alkyl chain by double hydrogen (H) atom abstraction using molecular O2. The reaction step studied here is presumably associated with the highest activation barrier along the full pathway; therefore, its quantitative assessment is of key importance to the understanding of the catalysis. The DMRG approach allows unprecedentedly large active spaces for the explicit correlation of electrons in the large part of the chemically important valence space, which is apparently conditio sine qua non for obtaining well-converged reaction energetics. The derived reaction mechanism involves protonation of the previously characterized 1,2-μ peroxy Fe(III)Fe(III) (P) intermediate to a 1,1-μ hydroperoxy species, which abstracts an H atom from the C10 site of the substrate. An Fe(IV)-oxo unit is generated concomitantly, supposedly capable of the second H atom abstraction from C9. In addition, several popular DFT functionals were compared to the computed DMRG-CASPT2 data. Notably, many of these show a preference for heterolytic C-H cleavage, erroneously predicting substrate hydroxylation. This study shows that, despite its limitations, DMRG-CASPT2 is a significant methodological advancement toward the accurate computational treatment of complex bioinorganic systems, such as those with the highly open-shell diiron active sites.
- Published
- 2014
27. Density matrix renormalization group forab initioCalculations and associated dynamic correlation methods: A review of theory and applications
- Author
-
Yuki Kurashige, Tran Nguyen Lan, Masaaki Saitow, Wataru Mizukami, Takeshi Yanai, and Jakub Chalupský
- Subjects
Physics ,Electronic correlation ,Density matrix renormalization group ,Ab initio ,Context (language use) ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Ab initio quantum chemistry methods ,Quantum electrodynamics ,Condensed Matter::Strongly Correlated Electrons ,Correlation method ,Configuration space ,Statistical physics ,Physical and Theoretical Chemistry ,Wave function - Abstract
The recent advent of the density matrix renormalization group (DMRG) theory has delivered a new capability to compute multireference (MR) wave function with large configuration space, which far exceeds the limitation of conventional approaches. Here, we provide an overview of our recent work on the developments of ab initio DMRG methods in the context of the active space approaches and their applications to MR chemical systems. © 2014 Wiley Periodicals, Inc.
- Published
- 2014
28. Multistate Complete-Active-Space Second-Order Perturbation Theory Based on Density Matrix Renormalization Group Reference States
- Author
-
Xiao-Gen Xiong, Jakub Chalupský, Masaaki Saitow, Sheng Guo, Sandeep Sharma, Yuki Kurashige, and Takeshi Yanai
- Subjects
010304 chemical physics ,Computational complexity theory ,Density matrix renormalization group ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Computer Science Applications ,Active space ,symbols.namesake ,RDM ,Computational chemistry ,0103 physical sciences ,symbols ,Reduced density matrix ,Statistical physics ,Complete active space ,Physical and Theoretical Chemistry ,Hamiltonian (quantum mechanics) ,Wave function ,Mathematics - Abstract
We present the development of the multistate multireference second-order perturbation theory (CASPT2) with multiroot references, which are described using the density matrix renormalization group (DMRG) method to handle a large active space. The multistate first-order wave functions are expanded into the internally contracted (IC) basis of the single-state single-reference (SS-SR) scheme, which is shown to be the most feasible variant to use DMRG references. The feasibility of the SS-SR scheme comes from two factors: first, it formally does not require the fourth-order transition reduced density matrix (TRDM) and second, the computational complexity scales linearly with the number of the reference states. The extended multistate (XMS) treatment is further incorporated, giving suited treatment of the zeroth-order Hamiltonian despite the fact that the SS-SR based IC basis is not invariant with respect to the XMS rotation. In addition, the state-specific fourth-order reduced density matrix (RDM) is eliminated in an approximate fashion using the cumulant reconstruction formula, as also done in the previous state-specific DMRG-cu(4)-CASPT2 approach. The resultant method, referred to as DMRG-cu(4)-XMS-CASPT2, uses the RDMs and TRDMs of up to third-order provided by the DMRG calculation. The multistate potential energy curves of the photoisomerization of diarylethene derivatives with CAS(26e,24o) are presented to illustrate the applicability of our theoretical approach.
- Published
- 2017
29. Toward Reliable Prediction of Hyperfine Coupling Constants Using Ab Initio Density Matrix Renormalization Group Method: Diatomic 2Σ and Vinyl Radicals as Test Cases
- Author
-
Yuki Kurashige, Tran Nguyen Lan, and Takeshi Yanai
- Subjects
Physics ,Valence (chemistry) ,Electronic correlation ,Atomic orbital ,Quantum mechanics ,Density matrix renormalization group ,Ab initio ,Complete active space ,Physical and Theoretical Chemistry ,Configuration interaction ,Molecular physics ,Diatomic molecule ,Computer Science Applications - Abstract
The density matrix renormalization group (DMRG) method is used in conjunction with the complete active space (CAS) procedure, the CAS configuration interaction (CASCI), and the CAS self-consistent field (CASSCF) to evaluate hyperfine coupling constants (HFCCs) for a series of diatomic (2)Σ radicals (BO, CO(+), CN, and AlO) and vinyl (C2H3) radical. The electron correlation effects on the computed HFCC values were systematically investigated using various levels of active space, which were increasingly extended from single valence space to large-size model space entailing double valence and at least single polarization shells. In addition, the core correlation was treated by including the core orbitals in active space. Reasonably accurate results were obtained by the DMRG-CASSCF method involving orbital optimization, while DMRG-CASCI calculations with Hartree-Fock orbitals provided poor agreement of the HFCCs with the experimental values. To achieve further insights into the accuracy of HFCC calculations, the orbital contributions to the total spin density were analyzed at a given nucleus, which is directly related to the FC term and is numerically sensitive to the level of correlation treatment and basis sets. The convergence of calculated HFCCs with an increasing number of renormalized states was also assessed. This work serves as the first study on the performance of the ab initio DMRG method for HFCC prediction.
- Published
- 2014
30. Multireference electron correlation methods with density matrix renormalisation group reference functions
- Author
-
Yuki Kurashige
- Subjects
Condensed Matter::Quantum Gases ,Density matrix ,Electronic correlation ,Basis (linear algebra) ,Chemistry ,Group (mathematics) ,Density matrix renormalization group ,Biophysics ,Electronic structure ,Condensed Matter Physics ,Potential energy ,Excited state ,Quantum electrodynamics ,Quantum mechanics ,Condensed Matter::Strongly Correlated Electrons ,Physical and Theoretical Chemistry ,Molecular Biology - Abstract
Recent advances in quantum chemical density matrix renormalisation group (DMRG) theory are presented. The DMRG, originally devised as an alternative to the exact diagonalisation in condensed matter physics, has become a powerful quantum chemical method for molecular systems that exhibit a multireference character, e.g., excited states, π-conjugated systems, transition metal complexes, and in particular for large systems by combining it with conventional multireference electron correlation methods. The capability of the current quantum chemical DMRG is demonstrated for an application involving the potential energy curve of the chromium dimer, which is one of the most demanding multireference systems and thus requires the best electronic structure treatment for non-dynamical and dynamical correlation as well as large basis sets.
- Published
- 2013
31. Matrix product state formulation of the multiconfiguration time-dependent Hartree theory
- Author
-
Yuki Kurashige, Department of Chemistry, Kyoto University, and Kyoto University [Kyoto]
- Subjects
Quantum dynamics ,Computer Science::Neural and Evolutionary Computation ,FOS: Physical sciences ,General Physics and Astronomy ,01 natural sciences ,Projection (linear algebra) ,symbols.namesake ,MCTDH ,Variational principle ,Physics - Chemical Physics ,0103 physical sciences ,Tangent space ,[CHIM]Chemical Sciences ,Applied mathematics ,Physics::Atomic Physics ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,010306 general physics ,ComputingMilieux_MISCELLANEOUS ,Matrix product state ,Ansatz ,Chemical Physics (physics.chem-ph) ,[PHYS]Physics [physics] ,Physics ,Quantum Physics ,010304 chemical physics ,Hilbert space ,Hartree ,16. Peace & justice ,symbols ,Quantum Physics (quant-ph) - Abstract
A matrix product state formulation of the multiconfiguration time-dependent Hartree (MPS-MCTDH) theory is presented. The Hilbert space that is spanned by the direct products of the phonon degree of freedoms, which is linearly parameterized in the MCTDH ansatz and thus results in an exponential increase of the computational cost, is parametrized by the MPS form. Equations of motion based on the Dirac-Frenkel time-dependent variational principle is derived by using the tangent space projection and the projector-splitting technique for the MPS, which have been recently developed. The mean-field operators, which appears in the equation of motion of the MCTDH single particle functions, are written in terms of the MPS form and efficiently evaluated by a sweep algorithm that is similar to the DMRG sweep. The efficiency and convergence of the MPS formulation to the MCTDH are demonstrated by quantum dynamics simulations of extended excitonic molecular systems., 9 pages, 1figure
- Published
- 2018
32. Theoretical Study of the π → π* Excited States of Oligoacenes: A Full π-Valence DMRG-CASPT2 Study
- Author
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Yuki Kurashige and Takeshi Yanai
- Subjects
Anthracene ,chemistry.chemical_compound ,Valence (chemistry) ,chemistry ,Excited state ,Density matrix renormalization group ,General Chemistry ,Complete active space ,Atomic physics ,Hexacene - Abstract
The energy levels of low-lying π → π* excited states of oligoacenes, anthracene to hexacene, were studied by using the DMRG-CASPT2 method with a full π-valence complete active space. The effects of...
- Published
- 2014
33. Multireference Ab Initio Density Matrix Renormalization Group (DMRG)-CASSCF and DMRG-CASPT2 Study on the Photochromic Ring Opening of Spiropyran
- Author
-
Keiji Morokuma, Takeshi Yanai, Fengyi Liu, and Yuki Kurashige
- Subjects
Spiropyran ,Density matrix renormalization group ,Ab initio ,Basis function ,Energy minimization ,Computer Science Applications ,chemistry.chemical_compound ,Molecular geometry ,chemistry ,Quantum mechanics ,Excited state ,Condensed Matter::Strongly Correlated Electrons ,Physical and Theoretical Chemistry ,Wave function - Abstract
The photochromic ring-opening reaction of spiropyran has been revisited at the multireference CASSCF and CASPT2 level with a CAS(22e,20o) active space, in combination with density matrix renormalization group (DMRG) methods. The accuracy of the DMRG-CASSCF and DMRG-CASPT2 calculations, with respect to the number of renormalized states, the number of roots in state-averaged wave functions, and the number basis functions, was examined. For the current system, chemically accurate results can be obtained with a relatively small number of renormalized states. The nature and vertical excitation energies of the excited (S1 and S2) states are consistent with conventional CAS(or RAS)PT2 with medium active spaces. The capability of the DMRG-CASSCF method in the optimization of molecular geometry is demonstrated for the first time. The computation costs (several hours per optimization cycle) are comparable with that of the conventional CASSCF geometry optimization with small active space. Finally, the DMRG-PT2 computed S1-MEP for the C-O and C-N bond-cleavage processes show good agreement with our previous calculations with a CAS(12e,10o) active space [Liu, F.; Morokuma, K. J. Am. Chem. Soc. 2013, 135, 10693-10702]. Especially, the role of the HOOP valleys in the S1 → S0 nonadiabatic decay has been confirmed.
- Published
- 2013
34. Entangled quantum electronic wavefunctions of the Mn4CaO5 cluster in photosystem II
- Author
-
Takeshi Yanai, Yuki Kurashige, and Garnet Kin-Lic Chan
- Subjects
Physics ,Quantum state ,General Chemical Engineering ,Quantum mechanics ,Density matrix renormalization group ,Cluster (physics) ,Density functional theory ,General Chemistry ,Quantum entanglement ,Wave function ,Quantum ,Spin-½ - Abstract
It is a long-standing goal to understand the reaction mechanisms of catalytic metalloenzymes at an entangled many-electron level, but this is hampered by the exponential complexity of quantum mechanics. Here, by exploiting the special structure of physical quantum states and using the density matrix renormalization group, we compute near-exact many-electron wavefunctions of the Mn_4CaO_5 cluster of photosystem II, with more than 1 × 10^(18) quantum degrees of freedom. This is the first treatment of photosystem II beyond the single-electron picture of density functional theory. Our calculations support recent modifications to the structure determined by X-ray crystallography. We further identify multiple low-lying energy surfaces associated with the structural distortion seen using X-ray crystallography, highlighting multistate reactivity in the chemistry of the cluster. Direct determination of Mn spin-projections from our wavefunctions suggests that current candidates that have been recently distinguished using parameterized spin models should be reassessed. Through entanglement maps, we reveal rich information contained in the wavefunctions on bonding changes in the cycle.
- Published
- 2013
35. More π Electrons Make a Difference: Emergence of Many Radicals on Graphene Nanoribbons Studied by Ab Initio DMRG Theory
- Author
-
Wataru Mizukami, Yuki Kurashige, and Takeshi Yanai
- Subjects
Organic semiconductor ,Mesoscopic physics ,Zigzag ,Condensed matter physics ,Chemistry ,Density matrix renormalization group ,Ab initio ,Electron ,Physical and Theoretical Chemistry ,Quantum ,Graphene nanoribbons ,Computer Science Applications - Abstract
Graphene nanoribbons (GNRs), also seen as rectangular polycyclic aromatic hydrocarbons, have been intensively studied to explore their potential applicability as superior organic semiconductors with high mobility. The difficulty arises in the synthesis or isolation of GNRs with increased conjugate length, GNRs being known to have radical electrons on their zigzag edges. Here, we use a most advanced ab initio theory based on density matrix renormalization group (DMRG) theory to show the emerging process of how GNRs develop electronic states from nonradical to radical characters with increasing ribbon length. We show the mesoscopic size effect that comes into play in quantum many-body interactions of π electrons, which is responsible for the polyradical nature. An analytic form is presented to model the size dependence of the number of radicals for arbitrary-length GNRs. These results and associated insights deepen the understanding of carbon-based chemistry and offer useful information for the synthesis and design of stable and functional GNRs.
- Published
- 2012
36. Coherent singlet fission activated by symmetry breaking
- Author
-
Yuki Kurashige, Kiyoshi Miyata, Takeshi Yanai, Yoshiyasu Matsumoto, Shunsuke Tanaka, Toshiki Sugimoto, Kazuya Watanabe, Shota Takahashi, and Jun Takeya
- Subjects
Chemistry ,General Chemical Engineering ,Exciton ,02 engineering and technology ,General Chemistry ,Conical intersection ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Potential energy ,0104 chemical sciences ,Excited state ,Singlet fission ,Potential energy surface ,Symmetry breaking ,0210 nano-technology ,Excitation - Abstract
Singlet fission, in which a singlet exciton is converted to two triplet excitons, is a process that could be beneficial in photovoltaic applications. A full understanding of the dynamics of singlet fission in molecular systems requires detailed knowledge of the relevant potential energy surfaces and their (conical) intersections. However, obtaining such information is a nontrivial task, particularly for molecular aggregates. Here we investigate singlet fission in rubrene crystals using transient absorption spectroscopy and state-of-the-art quantum chemical calculations. We observe a coherent and ultrafast singlet-fission channel as well as the well-known and conventional thermally assisted incoherent channel. This coherent channel is accessible because the conical intersection for singlet fission on the excited-state potential energy surface is located very close to the equilibrium position of the ground-state potential energy surface and also because of the excitation of an intermolecular symmetry-breaking mode, which activates the electronic coupling necessary for singlet fission.
- Published
- 2016
37. Computational Evidence of Inversion of (1)La and (1)Lb-Derived Excited States in Naphthalene Excimer Formation from ab Initio Multireference Theory with Large Active Space: DMRG-CASPT2 Study
- Author
-
Soichi Shirai, Yuki Kurashige, and Takeshi Yanai
- Subjects
Physics ,010304 chemical physics ,Electronic correlation ,Density matrix renormalization group ,Ab initio ,010402 general chemistry ,Excimer ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,Computer Science Applications ,Quantum mechanics ,Excited state ,Metastability ,0103 physical sciences ,Singlet state ,Physical and Theoretical Chemistry ,Ground state - Abstract
The naphthalene molecule has two important lowest-lying singlet excited states, denoted (1)La and (1)Lb. Association of the excited and ground state monomers yields a metastable excited dimer (excimer), which emits characteristic fluorescence. Here, we report a first computational result based on ab initio theory to corroborate that the naphthalene excimer fluorescence is (1)La parentage, resulting from inversion of (1)La and (1)Lb-derived dimer states. This inversion was hypothesized by earlier experimental studies; however, it has not been confirmed rigorously. In this study, the advanced multireference (MR) theory based on the density matrix renormalization group that enables using unprecedented large-size active space for describing significant electron correlation effects is used to provide accurate potential energy curves (PECs) of the excited states. The results evidenced the inversion of the PECs and accurately predicted transition energies for excimer fluorescence and monomer absorption. Traditional MR calculations with smaller active spaces and single-reference theory calculations exhibit serious inconsistencies with experimental observations.
- Published
- 2016
38. Accelerating convergence in iterative solution for large-scale complete active space self-consistent-field calculations
- Author
-
Yuki Kurashige, Garnet Kin-Lic Chan, Takeshi Yanai, and Debashree Ghosh
- Subjects
Physics ,Field (physics) ,Density matrix renormalization group ,Extrapolation ,Configuration interaction ,Condensed Matter Physics ,Space (mathematics) ,Atomic and Molecular Physics, and Optics ,Quantum mechanics ,Convergence (routing) ,Applied mathematics ,Complete active space ,Physical and Theoretical Chemistry ,Wave function - Abstract
An algorithm that accelerates the convergence of the iterative optimization of the complete active space self-consistent field (CASSCF) wavefunction so as to find a optimum solution in fewer macroiterations is described. The algorithm is oriented to large-scale CASSCF problems that are to be solved with a combination of density matrix renormalization group (DMRG) method for the configuration interaction (CI) process. The algorithm is based on the alternating (or two-step) CASSCF optimization in which the CI and molecular orbital (MO) parameters are optimized separately. Convergence ratio is improved by finding further optimized MOs from a linear extrapolation of the MO sets of the iteration history. The acceleration results in fewer diagonalizations in a total CASSCF calculation to save a considerable computational cost. The convergence performance is examined in a couple of realistic applications on SiC3 and poly(phenyl)carbenes. For poly(phenyl)carbenes, the large-size CASSCF calculations with CAS(30e,30o) that entails full π valence space as well as sp2 orbital space of carbenes are performed by using the practical implementation of DMRG-CASSCF in conjunction with the acceleration technique.
- Published
- 2009
39. The most stable structure of SiC3 studied by multireference perturbation theory with general multiconfiguration self-consistent field reference functions
- Author
-
Yuki Kurashige, Haruyuki Nakano, and Kimihiko Hirao
- Subjects
Carbon -- Research ,Carbon -- Structure ,Silicon -- Research ,Silicon -- Structure ,Chemistry, Physical and theoretical -- Analysis ,Chemicals, plastics and rubber industries - Abstract
The second-order perturbation theory with general multiconfiguration self-consistent field reference functions (GMC-PT) and Dunning's augmented correlation-consistent polarized valence quadruple- zeta (aug-cc-pVQZ) basis set is used to investigate the most stable structure of the SiC3 molecule. The results showed that a closed-shell rhomboidal C(super 2v) isomer with a C-C transannular bond (2s) was most stable.
- Published
- 2004
40. A pentanuclear iron catalyst designed for water oxidation
- Author
-
Ko Yoneda, Takeshi Yanai, Reiko Kuga, Shigeyuki Masaoka, Masaki Yoshida, Satoshi Kawata, Vijayendran K. K. Praneeth, Yuki Kurashige, Shinya Hayami, Mio Kondo, and Masaya Okamura
- Subjects
Multidisciplinary ,Electrolysis of water ,010405 organic chemistry ,Chemistry ,Inorganic chemistry ,Overpotential ,010402 general chemistry ,Electrocatalyst ,Electrochemistry ,01 natural sciences ,Redox ,0104 chemical sciences ,Catalysis ,Transition metal ,Oxidizing agent - Abstract
Although the oxidation of water is efficiently catalysed by the oxygen-evolving complex in photosystem II (refs 1 and 2), it remains one of the main bottlenecks when aiming for synthetic chemical fuel production powered by sunlight or electricity. Consequently, the development of active and stable water oxidation catalysts is crucial, with heterogeneous systems considered more suitable for practical use and their homogeneous counterparts more suitable for targeted, molecular-level design guided by mechanistic understanding. Research into the mechanism of water oxidation has resulted in a range of synthetic molecular catalysts, yet there remains much interest in systems that use abundant, inexpensive and environmentally benign metals such as iron (the most abundant transition metal in the Earth's crust and found in natural and synthetic oxidation catalysts). Water oxidation catalysts based on mononuclear iron complexes have been explored, but they often deactivate rapidly and exhibit relatively low activities. Here we report a pentanuclear iron complex that efficiently and robustly catalyses water oxidation with a turnover frequency of 1,900 per second, which is about three orders of magnitude larger than that of other iron-based catalysts. Electrochemical analysis confirms the redox flexibility of the system, characterized by six different oxidation states between Fe(II)5 and Fe(III)5; the Fe(III)5 state is active for oxidizing water. Quantum chemistry calculations indicate that the presence of adjacent active sites facilitates O-O bond formation with a reaction barrier of less than ten kilocalories per mole. Although the need for a high overpotential and the inability to operate in water-rich solutions limit the practicality of the present system, our findings clearly indicate that efficient water oxidation catalysts based on iron complexes can be created by ensuring that the system has redox flexibility and contains adjacent water-activation sites.
- Published
- 2015
41. Multinuclear metal-binding ability of a carotene
- Author
-
Yuki Kurashige, Shinnosuke Horiuchi, Mitsuki Yamashita, Teruo Matsutani, Takeshi Yanai, Kohei Takase, Tetsuro Murahashi, Shiori Kawamata, Koji Yamamoto, Yuki Tachibana, and Kohei Masai
- Subjects
Magnetic Resonance Spectroscopy ,medicine.medical_treatment ,Molecular Conformation ,General Physics and Astronomy ,Crystallography, X-Ray ,Article ,General Biochemistry, Genetics and Molecular Biology ,Molecular conformation ,Metal ,Coordination Complexes ,medicine ,Reactivity (chemistry) ,Chelating Agents ,Platinum ,chemistry.chemical_classification ,Multidisciplinary ,Chemistry ,Metal binding ,Carotene ,General Chemistry ,Nuclear magnetic resonance spectroscopy ,beta Carotene ,Combinatorial chemistry ,Biochemistry ,visual_art ,Unsaturated hydrocarbon ,visual_art.visual_art_medium ,Palladium - Abstract
Carotenes are naturally abundant unsaturated hydrocarbon pigments, and their fascinating physical and chemical properties have been studied intensively not only for better understanding of the roles in biological processes but also for the use in artificial chemical systems. However, their metal-binding ability has been virtually unexplored. Here we report that β-carotene has the ability to assemble and align ten metal atoms to afford decanuclear homo- and heterometal chain complexes. The metallo–carotenoid framework shows reversible metalation–demetalation reactivity with multiple metals, which allows us to control the size of metal chains as well as the heterobimetallic composition and arrangement of the carotene-supported metal chains., Carotenes are naturally abundant, widely studied unsaturated hydrocarbon pigments but their metal-binding ability has been virtually unexplored. Here, the authors demonstrate that they can be used to reversibly assemble and align homo- and hetero-metallic decanuclear chain complexes.
- Published
- 2015
42. Adaptive density partitioning technique in the auxiliary plane wave method
- Author
-
Yuki Kurashige, Kimihiko Hirao, and Takahito Nakajima
- Subjects
Physics ,Basis (linear algebra) ,Gaussian ,Mathematical analysis ,Plane wave ,General Physics and Astronomy ,Bottleneck ,Core (optical fiber) ,Matrix (mathematics) ,symbols.namesake ,Computational chemistry ,Coulomb ,symbols ,Physical and Theoretical Chemistry ,Representation (mathematics) - Abstract
We have developed the adaptive density partitioning technique (ADPT) in the auxiliary plane wave method, in which a part of the density is expanded to plane waves, for the fast evaluation of Coulomb matrix. Our partitioning is based on the error estimations and allows us to control the accuracy and efficiency. Moreover, we can drastically reduce the core Gaussian products that are left in Gaussian representation (its analytical integrals is the bottleneck in this method). For the taxol molecule with 6-31G** basis, the core Gaussian products accounted only for 5% in submicrohartree error.
- Published
- 2006
43. Reactivity of the binuclear non-heme iron active site of Δ⁹ desaturase studied by large-scale multireference ab initio calculations
- Author
-
Jakub, Chalupský, Tibor András, Rokob, Yuki, Kurashige, Takeshi, Yanai, Edward I, Solomon, Lubomír, Rulíšek, and Martin, Srnec
- Subjects
Models, Molecular ,Catalytic Domain ,Iron ,Quantum Theory ,Thermodynamics ,Stearoyl-CoA Desaturase - Abstract
The results of density matrix renormalization group complete active space self-consistent field (DMRG-CASSCF) and second-order perturbation theory (DMRG-CASPT2) calculations are presented on various structural alternatives for the O-O and first C-H activating step of the catalytic cycle of the binuclear nonheme iron enzyme Δ(9) desaturase. This enzyme is capable of inserting a double bond into an alkyl chain by double hydrogen (H) atom abstraction using molecular O2. The reaction step studied here is presumably associated with the highest activation barrier along the full pathway; therefore, its quantitative assessment is of key importance to the understanding of the catalysis. The DMRG approach allows unprecedentedly large active spaces for the explicit correlation of electrons in the large part of the chemically important valence space, which is apparently conditio sine qua non for obtaining well-converged reaction energetics. The derived reaction mechanism involves protonation of the previously characterized 1,2-μ peroxy Fe(III)Fe(III) (P) intermediate to a 1,1-μ hydroperoxy species, which abstracts an H atom from the C10 site of the substrate. An Fe(IV)-oxo unit is generated concomitantly, supposedly capable of the second H atom abstraction from C9. In addition, several popular DFT functionals were compared to the computed DMRG-CASPT2 data. Notably, many of these show a preference for heterolytic C-H cleavage, erroneously predicting substrate hydroxylation. This study shows that, despite its limitations, DMRG-CASPT2 is a significant methodological advancement toward the accurate computational treatment of complex bioinorganic systems, such as those with the highly open-shell diiron active sites.
- Published
- 2014
44. The π → π* excited states of long linear polyenes studied by the CASCI-MRMP method
- Author
-
Yuki Kurashige, Kimihiko Hirao, Yoshihide Nakao, and Haruyuki Nakano
- Subjects
Physics ,Valence (chemistry) ,business.industry ,General Physics and Astronomy ,Ionic bonding ,Configuration interaction ,Covalent bond ,Excited state ,Optoelectronics ,Complete active space ,Singlet state ,Physical and Theoretical Chemistry ,Atomic physics ,business - Abstract
Multireference Moller–Plesset perturbation theory with complete active space configuration interaction (CASCI-MRMP) is applied to the study of the valence π → π* excited states of all-trans linear polyenes C2nH2n+2 (n = 3–14). Our focus was to determine the nature of the four lowest-lying singlet excited states, 2 1 A g - , 1 1 B u + , 1 1 B u - and 3 1 A g - and their ordering. The ionic 1 1 B u + state is the lowest optically allowed excited state, while the covalent 2 1 A g - , 1 1 B u - and 3 1 A g - states are the optically forbidden states. Theory predicts that the 1 1 B u - state becomes lower than the 1 1 B u + state at n ⩾ 7 and that the 3 1 A g - state also becomes lower than the 1 1 B u + state at n ⩾ 11.
- Published
- 2004
45. The Most Stable Structure of SiC3 Studied by Multireference Perturbation Theory with General Multiconfiguration Self-Consistent Field Reference Functions
- Author
-
Kimihiko Hirao, Haruyuki Nakano, and Yuki Kurashige
- Subjects
Coupled cluster ,Valence (chemistry) ,Chemistry ,Molecule ,Perturbation theory (quantum mechanics) ,Physical and Theoretical Chemistry ,Self consistent ,Atomic physics ,Basis set - Abstract
The most stable structure of the SiC 3 molecule has been investigated using second-order perturbation theory with general multiconfiguration self-consistent field reference functions (GMC-PT) and Dunning's augmented correlation-consistent polarized valence quadruple-ζ (aug-cc-pVQZ) basis set. The results showed that a closed-shell rhomboidal C 2 v isomer with a C-C transannular bond (2s) was most stable. Another closed-shell rhomboidal C 2 v isomer with a Si-C transannular bond (3s) and a linear triplet Si-C-C-C isomer (1t) was less stable by 5.3 and 6.7 kcal/mol, respectively, at the geometries optimized by the coupled cluster singles, doubles, and perturbative triples (CCSD(T)) method and the correlation-consistent polarized core-valence quadruple-ζ (cc-pCVQZ) basis set, and by 9.0 and 9.9 kcal/mol, respectively, at the geometries optimized by the fully optimized reaction space self-consistent field (FORS-SCF) method and the 6-31G(d) basis set.
- Published
- 2004
46. Radical O-O coupling reaction in diferrate-mediated water oxidation studied using multireference wave function theory
- Author
-
Yuki Kurashige, Takeshi Yanai, Masaaki Saitow, and Jakub Chalupský
- Subjects
Chemistry ,Potassium Compounds ,Density matrix renormalization group ,Ab initio ,General Physics and Astronomy ,Multireference configuration interaction ,Water ,Electronic structure ,Oxygen ,Kinetics ,Chemical physics ,Computational chemistry ,Intramolecular force ,Kinetic isotope effect ,Complete active space ,Physical and Theoretical Chemistry ,Wave function ,Oxidation-Reduction ,Iron Compounds - Abstract
The O–O (oxygen–oxygen) bond formation is widely recognized as a key step of the catalytic reaction of dioxygen evolution from water. Recently, the water oxidation catalyzed by potassium ferrate (K2FeO4) was investigated on the basis of experimental kinetic isotope effect analysis assisted by density functional calculations, revealing the intramolecular oxo-coupling mechanism within a di-iron(VI) intermediate, or diferrate [Sarma et al., J. Am. Chem. Soc., 2012, 134, 15371]. Here, we report a detailed examination of this diferrate-mediated O–O bond formation using scalable multireference electronic structure theory. High-dimensional correlated many-electron wave functions beyond the one-electron picture were computed using the ab initio density matrix renormalization group (DMRG) method along the O–O bond formation pathway. The necessity of using large active space arises from the description of complex electronic interactions and varying redox states both associated with two-center antiferromagnetic multivalent iron–oxo coupling. Dynamic correlation effects on top of the active space DMRG wave functions were additively accounted for by complete active space second-order perturbation (CASPT2) and multireference configuration interaction (MRCI) based methods, which were recently introduced by our group. These multireference methods were capable of handling the double shell effects in the extended active space treatment. The calculations with an active space of 36 electrons in 32 orbitals, which is far over conventional limitation, provide a quantitatively reliable prediction of potential energy profiles and confirmed the viability of the direct oxo coupling. The bonding nature of Fe–O and dual bonding character of O–O are discussed using natural orbitals.
- Published
- 2014
47. 110 Effect of rolling conditions on microstructures and mechanical properties of Mg-Al-Ca-Mn alloy sheets
- Author
-
Shigeharu Kamado, Nozomu Kawabe, Yuki Kurashige, Katsuhito Yoshida, Takuya Matsumoto, Taiki Nakata, and Kazuha Suzawa
- Subjects
Materials science ,Annealing (metallurgy) ,Metallurgy ,Isotropy ,Recrystallization (metallurgy) - Published
- 2015
48. Multireference configuration interaction theory using cumulant reconstruction with internal contraction of density matrix renormalization group wave function
- Author
-
Masaaki Saitow, Yuki Kurashige, and Takeshi Yanai
- Subjects
Physics ,Hamiltonian matrix ,RDM ,Quantum electrodynamics ,Density matrix renormalization group ,General Physics and Astronomy ,Multireference configuration interaction ,Density functional theory ,Statistical physics ,Physical and Theoretical Chemistry ,Wave function ,Contraction (operator theory) ,Ansatz - Abstract
We report development of the multireference configuration interaction (MRCI) method that can use active space scalable to much larger size references than has previously been possible. The recent development of the density matrix renormalization group (DMRG) method in multireference quantum chemistry offers the ability to describe static correlation in a large active space. The present MRCI method provides a critical correction to the DMRG reference by including high-level dynamic correlation through the CI treatment. When the DMRG and MRCI theories are combined (DMRG-MRCI), the full internal contraction of the reference in the MRCI ansatz, including contraction of semi-internal states, plays a central role. However, it is thought to involve formidable complexity because of the presence of the five-particle rank reduced-density matrix (RDM) in the Hamiltonian matrix elements. To address this complexity, we express the Hamiltonian matrix using commutators, which allows the five-particle rank RDM to be canceled out without any approximation. Then we introduce an approximation to the four-particle rank RDM by using a cumulant reconstruction from lower-particle rank RDMs. A computer-aided approach is employed to derive the exceedingly complex equations of the MRCI in tensor-contracted form and to implement them into an efficient parallel computer code. This approach extends to the size-consistency-corrected variants of MRCI, such as the MRCI+Q, MR-ACPF, and MR-AQCC methods. We demonstrate the capability of the DMRG-MRCI method in several benchmark applications, including the evaluation of single-triplet gap of free-base porphyrin using 24 active orbitals.
- Published
- 2013
49. Entangled quantum electronic wavefunctions of the Mn₄CaO₅ cluster in photosystem II
- Author
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Yuki, Kurashige, Garnet Kin-Lic, Chan, and Takeshi, Yanai
- Subjects
Models, Molecular ,Manganese ,Photosystem II Protein Complex ,Quantum Theory ,Oxides ,Calcium Compounds - Abstract
It is a long-standing goal to understand the reaction mechanisms of catalytic metalloenzymes at an entangled many-electron level, but this is hampered by the exponential complexity of quantum mechanics. Here, by exploiting the special structure of physical quantum states and using the density matrix renormalization group, we compute near-exact many-electron wavefunctions of the Mn4CaO5 cluster of photosystem II, with more than 1 × 10(18) quantum degrees of freedom. This is the first treatment of photosystem II beyond the single-electron picture of density functional theory. Our calculations support recent modifications to the structure determined by X-ray crystallography. We further identify multiple low-lying energy surfaces associated with the structural distortion seen using X-ray crystallography, highlighting multistate reactivity in the chemistry of the cluster. Direct determination of Mn spin-projections from our wavefunctions suggests that current candidates that have been recently distinguished using parameterized spin models should be reassessed. Through entanglement maps, we reveal rich information contained in the wavefunctions on bonding changes in the cycle.
- Published
- 2012
50. Organic Photovoltaics: Singlet Fission of Non-polycyclic Aromatic Molecules in Organic Photovoltaics (Adv. Mater. 8/2016)
- Author
-
Yong-Jin Pu, Teruo Beppu, Masaki Hada, So Kawata, Ayaka Saito, Yuki Kurashige, Junji Kido, and Hiroshi Katagiri
- Subjects
Materials science ,010304 chemical physics ,Organic solar cell ,Mechanics of Materials ,Mechanical Engineering ,0103 physical sciences ,Singlet fission ,Molecule ,General Materials Science ,010402 general chemistry ,Photochemistry ,01 natural sciences ,0104 chemical sciences - Published
- 2016
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