Abstract: Electronic spectra for the first 275-nm absorption system of phenyl isocyanate observed in a room temperature and in a jet were assigned with an assistance of quantum-chemistry calculation. All vibronic bands in a jet were diffuse with a width of 18 cm⁻¹, indicating the lower limit of the life time was 204 fs. A suitable pair of a theoretical method and a basis set was selected among combinations of B3LYP, CAM-B3LYP, and MP2 and 18 kinds of basis sets on the basis of molecular-orbital energies and the rotational constant spectroscopically observed. B3LYP/cc-pVTZ and B3YP/aug-cc-pVDZ gave us good results. Time-dependent calculation was performed by two pairs. It was found out that the 275-nm absorption system was assigned as the first ππ* and third excited state and that twonπ* states with a very small oscillator strength were lying in the infrared and visible region. The fast relaxation process observed in a jet was due to an internal conversion to two nπ* states.

We have been developing the ABINIT-MP program for fragment molecular orbital (FMO) calculations over 20 years. In 2021, the Open Version 2 series has started for large scale systems consisting of more than ten thousand fragments. This letter describes the current status of ABINIT-MP, including the speed-up as well as the situation of distributions over supercomputing facilities in Japan.

Catechins are the main constituents in tea and have attracted attention due to their antioxidant properties. In this letter, the redox potential of single electron transfer and the pK_a of proton transfer in (+)-catechin has been calculated at the B3LYP/6-31++G (d, p) level of theory with a recently developed scheme to evaluate the standard hydrogen electrode potential and redox potential. Our computational scheme reproduced the experimental redox potential and pK_a value well.

In this study, we propose the quantum algorithm based on the unitary coupled cluster linear response theory for excited-state calculations with single and double excitations, denoted as qUCCSD-LR. Instead of the standard eigenvalue-problem-based scheme, the algorithm utilizes the dynamical-polarizability-based scheme, where the pole relative to the frequency of an external electric field corresponds to an excited state. Numerical applications of the qUCCSD-LR method to H₂ could reproduce the dynamical polarizabilities, excitation energies and oscillator strengths obtained by the standard CCSD-LR method. Furthermore, potential energy curves for the double bond rotation in the ground and excited states of C₂H₄ were accurately calculated by the proposed method.

For middle molecule drug discovery, a coarse-grained model in which amino acid residues were treated with an amino acid pair interaction was investigated. To treat both natural and artificial types of amino acids and staples, new interaction potentials were developed by umbrella sampling. For any artificial types of amino acids, the amino acid its potential was similar enough was extracted by using our method applied the structure similarity.

We have formulated a scheme for calculating phonon band structure based on our previously proposed coarse-graining theory, under the periodic boundary conditions. This coarse-graining method is unique in that the dimension of the atomic displacement vectors is reduced, unlike conventional ones in which the atomic positions are consolidated. The scheme was applied to a cyclic water hexamer, to demonstrate that the normal-mode vibration frequencies calculated with a full-atom calculation at the ab initio level were successfully reproduced. Even when the interactions among distant molecules were neglected, the stiffness matrix also gave a satisfactory result. Further, we attempted to rebuild the stiffness matrix using the block elements obtained from the normal-mode calculations for some partially-frozen clusters.

For large output of polymer electrolyte fuel cells (PEFCs), the electrode reaction activity of the catalyst layer (CL) consisting of carbon supports, Pt nanoparticles, Nafion chains, and water should be improved. Experimentally, it is reported that when Ketjen black (KB) with meso pores is used as the carbon support, the output of PEFC increases and that the pore size of the KB support affects the electrode reaction activity of the Pt nanoparticles. Therefore, in the present study, to clarify the effect of pore size on the electrode reaction activity of the Pt nanoparticles, we constructed catalyst particle (CP) models in which the Pt nanoparticles are supported and Nafion chains are coated on the KB model and investigated the CP structures with a different pore size of the KB support by reactive molecular dynamics method. Regardless of the pore size, the Pt nanoparticles on the exterior of the pore are fully covered with the Nafion chains and the Pt nanoparticles in the interior of the pore are not covered with the Nafion chains. This result suggests that the Pt nanoparticles in the interior of the pore show high oxygen transport property that does not depend on the pore size. Furthermore, we evaluated the connectivity of the Nafion chains to H₂O molecules absorbed on the Pt nanoparticles on the exterior and in the interior of the pores because the Nafion chains conduct the protons to the H₂O molecules on the Pt nanoparticles. As the pore size increases, more Nafion chains penetrate the interior of the pore and contact with H₂O molecules on the Pt nanoparticles, because more Nafion chains are vertically distributed above the larger pore. Finally, these results propose that both high oxygen transport property and high electrode reaction activity are achieved over the Pt nanoparticles in the interior of the large pore of the KB support because the oxygen diffusion in the pore is not blocked by the Nafion chains and the large pore size promotes the formation of a proton conducting path composed of the Nafion chains, H₂O, and Pt nanoparticles.