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2. Ground and excited states of singlet, cation doublet, and anion doublet states of 0-benzoquinone: A theoretical study

Author

Honda, Yasushi, Hada, Masahiko, Ehara, Masahiro, and Nakatsuji, Hiroshi

Subjects
Excited state chemistry -- Research, Quinone -- Chemical properties, Benzene -- Chemical properties, Chemicals, plastics and rubber industries
Abstract

The singlet excited states and doublet ionized/electron-attached states of o-benzoquinone (o-BQ) are analyzed by using the symmetry adapted cluster (SAC)/SAC-configuration interaction (SAC-CI) method. The SAC-CI theoretical spectra have showed that it is essential to take electron correlation into account when describing the singlet and doublet excited states of o-BQ.

Published
2007

4. SAC and SAC-CI calculations of excitation and circular dichroism spectra of straight-chain and cyclic dichalcogens

Author

Seino, Junji, Honda, Yasushi, Hada, Masahiko, and Nakatsuji, Hiroshi

Subjects
Circular dichroism -- Analysis, Quantum chemistry -- Analysis, Chemicals, plastics and rubber industries
Abstract

Accurate quantum-chemical calculations of the excitation energies and the rotatory strengths of dichalcogens R-Ch-Ch-R (Ch = S, Se, Te) are performed with the symmetry adapted cluster (SAC) and SAC-configuration interaction (CI) methods. The first and second lowest bands have depended on the R-Ch-Ch-R dihedral angle and the calculated trends have agreed with two empirical rules, the [C.sub.2] rule and the quadrant rule.

Published
2006

7. Peralkylated tetrasilanes: conformational dependence of the photoelectron spectrum

Author

Fogarty, Heather A., Tsuji, Hayato, David, Donald E., Ottosson, Carl-Henrick, Ehara, Masahiro, Nakatsuji, Hiroshi, Tamao, Kohei, and Michl, Josef

Subjects
Chemistry, Physical and theoretical -- Research, Photoelectrons -- Physiological aspects, Silane -- Physiological aspects, Alkylation -- Physiological aspects, Polymers -- Physiological aspects, Chemicals, plastics and rubber industries
Published
2002

9. Heterolytic adsorption of H2 on ZnO(1010) surface: an ab initio SPC cluster model study

Author

Lu, Xin, Xu, Xin, Wang, Nanqin, Zhang, Qianer, Ehara, Masahiro, and Nakatsuji, Hiroshi

Subjects
Adsorption -- Research, Surface chemistry -- Research, Zinc oxide -- Research, Hydrogen -- Research, Chemicals, plastics and rubber industries
Abstract

The heterolytic adsorption of H2 on ZnO(1010) surface is examined using an ab initio embedded cluster technique. Results show that the heterolytic adsorption of H2 on ZnO(1010) surface is site-dependent and occurs only on Zn-O ion pairs with low coordination numbers. These include the pairs Zn2c-O3c, Zn3C-O2c and Zn2c-O2c. Computed adsorption heats and vibrational frequencies also showed good agreement with experimental data.

Published
1999

11. Preface

Author

Wójcik, Marek, Nakatsuji, Hiroshi, Kirtman, Bernard, and Ozaki, Yukihiro

Published
2018

13. Accuracy of Td-DFT in the Ultraviolet and Circular Dichroism Spectra of Deoxyguanosine and Uridine

Author

Miyahara, Tomoo and Nakatsuji, Hiroshi

Abstract

Accuracy of the time-dependent density functional theory (Td-DFT) was examined for the ultraviolet (UV) and circular dichroism (CD) spectra of deoxyguanosine (dG) and uridine, using 11 different DFT functionals and two different basis sets. The Td-DFT results of the UV and CD spectra were strongly dependent on the functionals used. The basis-set dependence was observed only for the CD spectral calculations. For the UV spectra, the B3LYP and PBE0 functionals gave relatively good results. For the CD spectra, the B3LYP and PBE0 with 6-311G(d,p) basis gave relatively permissible result only for dG. The results of other functionals were difficult to be used for the studies of the UV and CD spectra, though the symmetry adapted cluster–configuration interaction (SAC–CI) method reproduced well the experimental spectra of these molecules. To obtain valuable information from the theoretical calculations of the UV and CD spectra, the theoretical tool must be able to reproduce correctly both of the intensities and peak positions of the UV and CD spectra. Then, we can analyze the reasons of the changes of the intensity and/or the peak position to clarify the chemistry involved. It is difficult to recommend Td-DFT as such tools of science, at least from the examinations using dG and uridine.

Published
2024
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14. Keiji Morokuma

Author

Bowman, Joel M., primary, Musaev, Jamal, additional, and Nakatsuji, Hiroshi, additional

Published
2018
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17. Excited states of porphyrin isomers and porphycene derivatives: A SAC-CI study

Author

Hasegawa, Jun-ya, Takata, Koji, Miyahara, Tomoo, Neya, Saburo, Frisch, Michael J., and Nakatsuji, Hiroshi

Subjects
Porphyrins -- Structure, Porphyrins -- Properties, Isomerism -- Structure, Isomerism -- Properties, Density functionals -- Analysis, Chemicals, plastics and rubber industries
Abstract

Excited states of free-base porphyrin isomers, porphycene (Pc), corrphycene (Cor), and hemiporphycene (hPc), are studied by the Symmetry-Adapted Cluster (SAC)/SAC-Configuration Interaction (CI) method. The differences in the Q-band absorptions among the isomers are clearly explained by the four-orbital model.

Published
2005

19. Quasi-relativistic study of (super 199)Hg nuclear magnetic shielding constants of dimethylmercury, disiylmercury and digermylmercury

Author

Jian Wan, Fukuda, Ryoichi, Hada, Masahiko, and Nakatsuji, Hiroshi

Subjects
Bromine -- Research, Chemical reactions -- Observations, Iodine -- Research, Chlorine -- Research, Chemicals, plastics and rubber industries
Abstract

Quasi-relativistic ab initio calculations are performed for (super 199)Hg nuclear magnetic shielding constants and chemical shifts in a series, which included spin free relativistic (SFR) term and magnetic interaction (RMI) term. It is important to increase in the flexibility of the innermost and outermost orbitals of the basis set.

Published
2001

20. Variational calculations of fermion second-order reduced density matrices by semidefinite programming algorithm

Author

Nakata, Maho, Nakatsuji, Hiroshi, Ehara, Masahiro, FUKUDA, MITUHIRO, Fukuda, Mituhiro, Nakata, Kazuhide, and Fujisawa, Katsuki

Subjects
Semidefinite programming, Physics, Matrix algebra, Atoms in molecules, Convergence (routing), General Physics and Astronomy, Order (group theory), Reduced density matrix, Fermion, Physical and Theoretical Chemistry, Algorithm, Variable (mathematics)
Abstract

The ground-state fermion second-order reduced density matrix (2-RDM) is determined variationally using itself as a basic variable. As necessary conditions of the N-representability, we used the positive semidefiniteness conditions, P, Q, and G conditions that are described in terms of the 2-RDM. The variational calculations are performed by using recently developed semidefinite programming algorithm (SDPA). The calculated energies of various closed- and open-shell atoms and molecules are excellent, overshooting only slightly the full-CI energies. There was no case where convergence was not achieved. The calculated properties also reproduce well the full-CI results.

Published
2001

22. Electronic transitions in cis- and trans-dichloroethylenes and tetrachloroethylene

Author

Arulmozhiraja, Sundaram, Ehara, Masahiro, and Nakatsuji, Hiroshi

Subjects
molecule-photon collisions, triplet state, photodissociation, ultraviolet spectra, Rydberg states, molecular electronic states, organic compounds, configuration interactions
Abstract

Electronic structures of trans- and cis-dichloroethylenes and tetrachloroethylene were studied using symmetry-adapted cluster configuration interaction theory. Basis sets up to the aug-cc-pVTZ of Dunning, Jr., augmented with appropriate Rydberg functions were used for the calculations. The results derived in the present study show good agreement with the available experimental values. In all cases, the main bright excitation was the * transition. The other vertical excitations, *, n*, and n*, which have not been studied before, were also investigated. First Rydberg series involving transitions from the orbitals to one 3s, three 3p, and five 3d orbitals were identified clearly. Several new assignments and reassignments of features in the experimental spectra were suggested. Contrary to earlier prediction, two n-* states, along with a -* state in the dichloroethylenes, were calculated to be located above the main -* state. Accordingly, crossing between both the n-* states with the bright -* state is highly likely, unlike conclusions made in the earlier studies. This indicates that the photodissociation mechanism proposed by the earlier calculations warrants revision. Several low-lying triplet excited states were also studied. Electronic spectra of trans-1-chloro-2-fluoroethylene and cis-1-chloro-2-fluoroethylene were also calculated. The * transitions of these haloethylenes are compared and interpreted in terms of the inductive and resonance effects.

Published
2008

35. CircularDichroism Spectra of Uridine Derivatives: ChiraSac Study.

Author

Miyahara, Tomoo, Nakatsuji, Hiroshi, and Wada, Takehiko

Subjects
*CIRCULAR dichroism, *SPECTROSCOPE, *CONFORMERS (Chemistry), *URIDINE derivatives, *CHEMISTRY experiments, *ELECTRIC dipole moments
Abstract

Theexperimental circular dichroism (CD) spectra of uridine and NH2-uridinethat were different in the intensity and shape were studied in thelight of the ChiraSac method. The theoretical CD spectra at severaldifferent conformations using the symmetry-adapted-cluster configuration-interaction(SAC-CI) theory largely depended on the conformational angle, butthose of the anti-conformers and the Boltzmann average reproducedthe experimentally obtained CD spectra of both uridine and NH2-uridine.The differences in the CD spectra between the two uridine derivativeswere analyzed by using the angle θ between the electric transitiondipole moment (ETDM) and the magnetic transition dipole moment (MTDM). [ABSTRACT FROM AUTHOR]

Published
2014
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40. Helical Structure andCircular Dichroism Spectra ofDNA: A Theoretical Study.

Author

Miyahara, Tomoo, Nakatsuji, Hiroshi, and Sugiyama, Hiroshi

Subjects
*HELICAL structure, *CIRCULAR dichroism, *DNA spectra, *CONFORMATIONAL analysis, *HYDROGEN bonding, *CHEMISTRY experiments
Abstract

The helical structure is experimentally determined bycirculardichroism (CD) spectra. The sign and shape of the CD spectra are differentbetween B-DNA with a right-handed double-helical structure and Z-DNAwith a left-handed double-helical structure. In particular, the signat around 295 nm in CD spectra is positive for B-DNA, which is oppositeto that of Z-DNA. However, it is difficult to determine the helicalstructure from the UV absorption spectra. Three important factorsthat affect the CD spectra of DNA are (1) the conformation of dG monomer,(2) the hydrogen-bonding interaction between two helices, and (3)the stacking interaction between nucleic acid bases. We calculatedthe CD spectra of (1) the dG monomer at different conformations, (2)the composite of dG and dC monomers, (3) two dimer models that simulateseparately the hydrogen-bonding interaction and the stacking interaction,and (4) the tetramer model that includes both hydrogen-bonding andstacking interactions simultaneously. The helical structure of DNAcan be clarified by a comparison of the experimental and SAC-CI theoreticalCD spectra of DNA and that the sign at around 295 nm of the CD spectraof Z-DNA reflects from the strong stacking interaction characteristicof its helical structure. [ABSTRACT FROM AUTHOR]

Published
2013
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44. Dipped adcluster model study for the end-on chemisorption of O2on an Ag surface

Author

Nakatsuji, Hiroshi and Nakai, Hiromi

Abstract

Theoretical study for the end-on adsorption of an O2molecule on an Ag surface is carried out with the use of the dipped adcluster model (DAM). The adcluster of AgO2is taken and the highest spin coupling model is employed. Electron transfer from the bulk metal to the adcluster considered by DAM is important for the occurrence of the chemisorption, and this cannot be described by the small-size cluster model. Electron correlations are also quite important and are described by the SD-CI method based on the corresponding parent configurations. In the end-on geometry, the superoxide species is the ground state, and there are no peroxide species in the lower energy region. The calculated adsorption energy compares reasonably with the experimental value. The O—O axis of the superoxide is inclined by 70°–80° from the surface normal. The outside oxygen atom of the adsorbed species seems to be more reactive than the inside one, while the net charge on the former is smaller than that on the latter. Keywords: DAM (dipped adcluster model), silver, superoxide, chemisorption.

Published
1992
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45. Theoretical Study on the Decomposition of HCOOH on a ZnO(1010) Surface

Author

Yoshimoto, Masami, Takagi, Shinji, Umemura, Yoko, Hada, Masahiko, and Nakatsuji, Hiroshi

Abstract

The mechanism of the decomposition of formic acid HCOOH on ZnO(1010) surfaces was investigated using theab initiomolecular orbital method. Furthermore, the role of the dynamic bending of the surface formate anion HCOO−in the decomposition reaction was also examined. The lattice Zn atom interacts with the C–H bond of the adsorbed formate anion and cleaves the C–H bond to yield adsorbed CO2and ZnH species. However, similar results are not obtained with the lattice O atom or surface OH species. The energy barriers of C–H bond cleavage and CO2desorption from the surface were calculated to be 45.5 and 11.2 kcal/mol, respectively, at the MP2 level. H2formation is a bimolecular process: another formic acid from the gas phase attacks the ZnH surface species and produces an H2molecule. The calculated energy barrier is 2.2 kcal/mol and the exothermicity of the reaction is 11.3 kcal/mol at the MP2 level. These results indicate that the rate-determining step of the dehydrogenation decomposition of formic acid is cleavage of the C–H bond. Both the decomposition reaction and the dissociative adsorption of HCOOH occur more easily on hydrogen-covered surface than on a clean surface.

Published
1998
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50. Quantum Chemical Methods for Predicting and Interpreting Second-Order Nonlinear Optical Properties:from Small to Extended π-Conjugated Molecules

Author

Frédéric Castet, Marcelo Hidalgo Cardenuto, Marc de Wergifosse, Benoît Champagne, Pierre Beaujean, Vincent Liégeois, Wojcik, Marek, Nakatsuji, Hiroshi, Kirtman, Bernard, and Ozaki, Yokohiro

Subjects
first hyperpolarizability, solvation models, 010304 chemical physics, Electronic correlation, Chemistry, business.industry, Solvation, Hyperpolarizability, frequency dispersion, Function (mathematics), 010402 general chemistry, 01 natural sciences, basis sets, 0104 chemical sciences, Chemical physics, 0103 physical sciences, Density functional theory, Statistical physics, Photonics, wave function versus density functional theory methods, business, Wave function, Basis set
Abstract

This chapter addresses the methodological and computational aspects related to the prediction of molecular second-order nonlinear optical properties, i.e., the first hyperpolarizability (β), by using quantum chemistry methods. Both small (reference) molecules and extended push-pull π-conjugated systems are considered, highlighting contrasted effects about (i) the choice of a reliable basis set together with the convergence of β values as a function of the basis set size, (ii) the amplitude of electron correlation contributions and its estimate using wave function and density functional theory methods, (iii) the description of solvent effects using implicit and explicit solvation models, (iv) frequency dispersion effects in off-resonance conditions, and (v) numerical accuracy issues. When possible, comparisons with experiment are made. All in all, these results demonstrate that the calculations of β remain a challenge and that many issues need to be carefully addressed, pointing out difficulties toward elaborating black-box and computationally cheap protocols. Still, several strategies can be designed in order to achieve a targeted accuracy, either for reference molecules displaying small β responses or for molecules presenting large β values and a potential in optoelectronics and photonics.

Published
2018

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