Yu-ya Ohnishi

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We propose progressive downsampling of wave vectors in the Brillouin zone integrations occurring in the second-order many-body or Møller-Plesset perturbation (MP2) method for extended systems of one-dimensional periodicity. Higher-lying unoccupied and lower-lying occupied Bloch orbitals are subject to downsampling by an exponentially increasing factor (with(More)
A pedagogical, semi-rigorous proof is presented for the existence of the thermodynamic (infinite-volume) limit of the energy per volume for an electrically neutral, metallic or nonmetallic crystal. The proof is based on the demonstration of the same for individual energy components, namely, the kinetic, Coulomb, and exchange contributions to the(More)
The energies and wave functions of several lowest-lying vibrational states of FHF(-), ClHCl(-), and BrHBr(-) have been computed by a finite-difference method with and without the Born-Oppenheimer (BO) separation between the heavy (halogen) and light (hydrogen) particle motion. The so-called diagonal BO correction (DBOC), which includes the effect of the(More)
A hybrid of the coupled-cluster singles and doubles (CCSD) and second-order Møller-Plesset perturbation (MP2) methods [M. Nooijen, J. Chem. Phys. 111, 10815 (1999); A. D. Bochevarov and C. D. Sherrill, ibid. 122, 234110 (2005); A. D. Bochevarov et al., ibid. 125, 054109 (2006)] is formulated and implemented for one-dimensional periodic extended systems, in(More)
We report on the comparison of the electronic and photophysical properties of a series of related donor-acceptor-donor oligomers incorporating the previously known 2H-benzo[d][1,2,3]triazole (BTz) moiety as the acceptor and the recently reported BTzTD acceptor, a hybrid of BTz and 2,1,3-benzothiadiazole (BTD). Although often implied in the polymer(More)
Ruthenium-catalyzed hydrogenation of carbon dioxide to formic acid was theoretically investigated with DFT and MP4(SDQ) methods, where a real catalyst, cis-Ru(H)2(PMe3)3, was employed in calculations and compared with a model catalyst, cis-Ru(H)2(PH3)3. Significant differences between the real and model systems are observed in CO2 insertion into the(More)
Chemically reasonable models of PR3 (R = Me, Et, iPr, and tBu) were constructed to apply the post Hartree-Fock method to large transition metal complexes. In this model, R is replaced by the H atom including the frontier orbital consistent quantum capping potential (FOC-QCP) which reproduces the frontier orbital energy of PR3. The steric effect is(More)
Transmetalation between palladium(II)-vinyl complex and vinylsilane was theoretically investigated with the DFT and MP2 to MP4 methods to clarify the reaction mechanism and the reasons why fluoride anion accelerates the Pd-catalyzed cross-coupling reaction between vinyl iodide and vinylsilane. This transmetalation occurs with a very large activation barrier(More)
Theoretical and computational methods are powerful in studying transition metal complexes. Our theoretical studies of C-H sigma-bond activation of benzene by Pd(II)-formate complex and that of methane by Ti(IV)-imido complex successfully disclosed that these reactions are understood to undergo heterolytic sigma-bond activation and the driving force is the(More)
Explicitly correlated second-order Green's function (GF2-F12) is presented and applied to polycyclic aromatic hydrocarbons (PAHs), oligothiophene, and porphyrins. GF2 suffers from slow convergence of orbital expansions as in the ordinary post Hartree-Fock methods in ab initio theory, albeit the method is capable of providing quantitatively accurate(More)