Search

Au supported anatase TiO2enables the selective synthesis of propylene oxide from propylene using O2and H2. However, this reaction does not proceed on Au supported rutile TiO2. The origin of this difference in the catalytic activity was examined using DFT calculations. DFT calculations revealed that the stability of the TiOOH active species was directly related to the product selectivity.Au supported anatase TiO2enables the selective synthesis of propylene oxide from propylene using O2and H2, while this reaction does not proceed on Au supported rutile TiO2. This difference of the catalytic activity was examined using DFT calculation. From the calculation results, it was found that the stability of TiOOH is directly related to the product selectivity.

The charging speed of lithium-ion batteries can be enhanced by improving the diffusion performance of Li ions inside and at the interface of their cathodes. In this study, we applied strain to LiCoO2(LCO) cathode materials to elongate their lattices, and the relationship between the lattice strain and energy required for Li deintercalation, referred to as “Li vacancy formation energy,” was estimated by ab-initiocalculations to determine the optimal strain. The results suggest that the charging speed can be improved by adding a strain of less than 5% while retaining its high mechanical properties and equilibrium potential. Furthermore, we found that applying approximately 10% strain in the c-axis direction significantly reduces the Li vacancy formation energy of the LCO cathode.We applied strain to LiCoO2cathodes to elongate their lattices, and the relationship between the lattice strain and energy required for Li deintercalation was estimated by ab-initiocalculations. We found that the charging speed can be improved by adding a strain of less than 5% while retaining its high mechanical properties and equilibrium potential.

We investigated and compared various mechanical properties of two major cathode materials (LiCoO2(LCO) and LiNi0.33Co0.33Mn0.33O2(NCM)), which are particularly susceptible to degradation among components of lithium-ion batteries. In this analysis, ab initiocalculations using density functional theory (DFT) are adopted. The plotting of stress-strain curves and mechanical characterization of Li-deintercalated structures are conducted in addition to conventional elastic tensor calculations. In this study, the elastic moduli (stiffness) of LCO and NCM are similar, however, the strength and durability of the NCM cathode in the c-axis direction are clearly lower than those of LCO. These approaches can be applied to the mechanical characterization of new promising cathodes in the future.We conducted various mechanical chcaracterization of two major cathode materials: LiCoO2(LCO) and LiNi0.33Co0.33Mn0.33O2(NCM) using ab-initiocalculations, including the plotting of stress-strain curves and mechanical characterization of Li-deintercalated structures. Our main results are that the stiffness of LCO and NCM are similar whereas the strength and durability of the NCM cathode are clearly lower than those of LCO.

In the application of density functional theory (DFT) calculations to LiCoO2(LCO) cathode material of lithium-ion batteries, this study investigates the differences between the obtained values for lattice constants, elastic constants, and stress-strain curves using different calculation condition such as exchange-correlation energy functionals; additionally, it attempts to improve the accuracy of the mechanical characterization of the DFT calculation. The results reveal that the adoption of Perdew-Wang (PW91) functional with dispersion corrections is better in the structural optimization of the DFT calculation for the LCO cathode compared with other calculation conditions, such as the adoption of Perdew-Burke-Ernzerhof (PBE) and revised PBE for solids (PBE-solid), which have been used in previous studies. The high accuracy of the lattice constant calculations in the structural optimization using PW91 results in a relatively high evaluation accuracy of the mechanical properties of these cathode materials. Additionally, a strong correlation between the lattice (or lattice volumes) and elastic constants is observed; evidently, a slight deviation in the lattice constants causes a relatively significant change in the elastic constants. In some of the calculation results for stress-strain curves, differences in the elastic limits (elastic regions) dependent on the selected exchange-correlation functionals are clearly observed.In the ab-initiocalculations using density functional theory, we estimate the mechanical properties of LiCoO2(LCO) cathode material and seek better exchange-correlation functionals. Our study reveals that the Perdew-Wang (PW91) functional is better in the structural optimization and estimation of mechanical properties of LCO compared with other functionals.

The isomerization of allyl alcohols over Au/NiO catalysts produces corresponding aldehydes with high selectivities, but the mechanism underlying this catalytic reaction remains unclear. We investigate the isomerization of allyl alcohols over NiO-supported Au10catalysts using density functional theory calculations. Based on these calculations, the presence of an open base site is critical for isomerization over Au/NiO catalysts, and the rate-determining step is the protonation of the β-carbon of the substrate.Graphical AbstractThe isomerization of allyl alcohols over Au/NiO catalysts produces corresponding aldehydes with high selectivities, but the mechanism underlying this catalytic reaction remains unclear. We investigate the isomerization of allyl alcohols over NiO-supported Au10 catalysts using density functional theory calculations. Based on DFT calculations, the presence of an open base site is critical for isomerization over Au/NiO catalysts, and the rate-determining step is the protonation of the β-carbon of the substrate.

This paper proposed using the linear response function (LRF) of Kohn-Sham orbitals for checking the convergence regarding thickness in periodic slab-and-vacuum model calculations. The effectiveness was demonstrated using the alkaline earth metal oxide (001) surface. The calculated LRF decreases and converges to zero toward the opposite side of a slab. The proposed LRF scheme can be used as a guide to judge convergence of the slab thickness.This paper proposed using the linear response function (LRF) of Kohn-Sham orbitals for checking the convergence regarding thickness in periodic slab-and-vacuum model calculations. The effectiveness was demonstrated using the alkaline earth metal oxide (001) surface. The calculated results showed that the proposed LRF scheme can be used as a guide to judge convergence of the slab thickness.

A machine learning potential that can describe the ethylene hydrogenation reaction on Pt surface has been developed. Using the obtained potential, path integral molecular dynamics of hydrogen on Pt surface and metadynamics of hydrogen adsorption on Pt surface in the presence or absence of ethylene were carried out. The results of metadynamics were compared with adsorption Gibbs energy obtained from a single point calculation. The temperature and pressure dependency of the hydrogen coverage on Pt surface were also calculated with high accuracy.A machine learning potential that can describe the ethylene hydrogenation reaction on Pt surface has been developed. Using the obtained potential, path integral molecular dynamics of hydrogen on Pt surface and meta-dynamics of hydrogen adsorption on Pt surface were carried out. The results of meta-dynamics were compared with adsorption Gibbs energy obtained from a single point calculation.

Numerous experimental reports have addressed the advantages of the Au@NiO core–shell catalyst in the synthesis of methyl methacrylate. However, its high activity toward the oxidation of 1-methoxy-2-methylprop-2-en-1-ol and its inability to be oxidized to MeOH has not been elucidated. Herein, the direct oxidative esterification by an Au@NiO core–shell catalyst was studied using density functional theory calculations. Accordingly, particular attention was given to the stabilities of the adsorbed species, activation barrier, and intermediates; furthermore, the role of the highly oxidized NiOxwas elucidated, which has been regarded as essential for the reaction. The results showed that the active oxygen species in the oxidized NiOx, such as O2, OOH, and OH, were stabilized on the NiO bonded to the Au. These stabilized species improved the activity and selectivity of the reaction. Furthermore, the Ni vacancy in the subsurface generates a strong basic site on the surface of the catalyst, which traps the substrate and diminishes the activation barrier.

Interactions between nanosized Au cluster models (Au rods, ribbons, and film) and rutile TiO2(110) modeled surfaces (stoichiometric: sTiO2, reduced: rTiO2, and Cl-adsorbed: Cl-rTiO2) were determined using density functional theory. The Au–Au bonds are weakened and the Au–Ti bonds are strengthened because the oxygen defect sites in rTiO2donate electrons to the nanosized Au models. These interactions suppress the aggregation of the nanosized Au models on the rTiO2surface. However, Cl atoms are more strongly adsorbed at the oxygen defect site of rTiO2than Au. The amount of transferred electrons from Cl-rTiO2to the nanosized Au models is smaller than that of rTiO2. Notably, the Au/Cl-rTiO2interactions are smaller than the Au/sTiO2interactions in two- and three-dimensional Au clusters. Thus, Cl atom adsorption onto the oxygen defect site decreases the Au/TiO2interaction, and the aggregation of the nanosized Au models easily proceeds on Cl-rTiO2. Hence, the Cl atom adsorption onto the oxygen defect site of the TiO2surface can be assumed as a reason for the residual Cl enhancement of Au aggregation on the TiO2surface during Au/TiO2catalyst preparation.The mechanism of suppression of Au cluster aggregation on TiO2surface by the oxygen defect site is clarified theoretically. Additionally, the mechanism of suppression of the oxygen defect effect by Cl is clarified; this can be assumed as a reason for the residual Cl enhancement of Au aggregation on the TiO2surface during Au/TiO2catalyst preparation.

Organic ferromagnets and advanced magneticmetals have received continued interest over many decades. The systematic investigation of open-shell radicals had been reported by Morita and co-workers. Especially, trioxotriangulene (TOT) as a pure organic radical source was expected to realize novel electrical and spin properties. Based on their experimental results, they pointed out that Br3TOT and (t-Bu)3TOT, which are two types of TOT-based crystals, have different electrical properties. In this study, we have attempted to investigate the origins of the novel properties of the two crystals from various points of view such as the shape of the TOT radicals, nature of stacking in the TOT column (sliding parallel versus antiparallel stacking), spatial interactions between neighboring pairs, various types of magnetic interactions (e.g., Jab, Ueff, and tab) between two radicals, nature of the diradical character (yand ysys) and related chemical indices (U, I), change in the binding energies with changing geometries, and electrical conductivity (i.e., I–Vcharacteristics) of Au–TOT–TOT–Au systems. Finally, it is concluded that the magnetic interactions in the column structure for the former crystal are more effectively controlled than those in the latter crystal. High electric conductivity can be expected for Br3TOT, whereas (t-Bu)3TOT is thought to be a normal antiferromagnetic insulator.

Phenalenyl, zethrene, and extended zethrene molecules were employed to study the change in electronic properties of graphene surfaces upon exposure to oxygen atmosphere. These hydrocarbons are the smallest systems that can be used to evaluate intermolecular interaction with triplet oxygen molecules. The phenalenyl radical can simulate the radical nature of an edge structure and defect site of graphene sheets. Zethrene and extended zethrene molecules (n= 0, 1, 2, 3, and 4), which possess open-singlet diradical character, are also good models for studying chemisorption phenomena. From the calculated results for phenalenyl, the reaction path from the dissociation limit to the final products was found with chemisorbed structures (SS1and SS2) and transition states (TS1, TS2, and TS3). Calculated adsorption energies were 7.72 (SS1) and 6.58 (SS2) kcal mol−1. An oxygen molecule can form a contact with phenalenyl radical in a weak chemisorption process, which is endothermic and has very low energy barriers to transition states. For the zethrene series, the diradical character index y, used to describe coupling between two radical spins, was evaluated using the broken symmetry approach. The values were 0.00, 0.01, 0.10, 0.23, and 0.32, for n= 0, 1, 2, 3, and 4, respectively. Although diradical nature was absent in ordinary zethrene, other extended zethrene molecules exhibited diradical character. The radical spin induced in phenalenyl unit A can contribute to the chemisorption of triplet oxygen molecules. The calculated adsorption energy for the first O2adsorption onto heptazethrene was 5.38 kcal mol−1. Concomitantly, the radical electron on unit B revived and played an important role in the radical activity. The required adsorption energy for the second O2adsorption became lower at −0.64 kcal mol−1.

To elucidate the differences in the catalytic activities of two different polymer-stabilized Au cluster catalysts, Au:PVP and Au:PAA in the aerobic oxidation of p-hydroxybenzyl alcohol, the characteristics of these two kinds of polymer-stabilized Au nanocluster (Au NC) catalysts were investigated theoretically. The results of DFT and MD calculations showed that the coordination structures of the polymers onto the Au cluster play an important role for this difference.

We review a recently developed ab initio multireference (MR)-density functional theory (DFT) approach based on the partially interacting reference systems. Instead of Kohn–Sham equations, we introduce the auxiliary CI equation with the effective DFT potential field. For practice, we classify electrons of the target system into valence electrons and other electrons. The former plays the quantum resonating feature of electronic structure of molecular species, while the latter affects the electronic properties via the effective correlation potential for the former electrons. The theoretical devices in our MR-DFT are introduced to avoid the double counting problem for any combination of a wavefunction and a correlation functional. Some numerical examples are presented.

We review the extended density functional theory (DFT), in which we make full use of the broken-symmetry feature of the Kohn–Sham (KS) DFT. The theory is based on the classification of broken-symmetry solutions of the Hartree–Fock theory, which has been developed by some precursors in the field “broken-symmetry quantum chemistry”. We describe the fundamental characteristics of the DFT based on generalized spin orbitals (GSOs) in relation to the extension of the constrained search region of DFT. In addition, some important applications, such as noncollinear magnetism of multicenter radicals and radical dissociation followed by spin rotations that are firstly enabled by the use of the GSO-DFT, are presented. Furthermore, future directions covering quantum fluctuations between several collective modes, ab initio molecular dynamics, and relativistic phenomena are also described from the viewpoint of search regions of the extended DFT.

We have firstly developed the ab initio linear combination of gaussian type orbital (LCGTO) program of generalized spin orbital (GSO) density functional theory (DFT) and applied it for multicenter metal clusters with noncollinear spin structures. It was found that two- and three-dimensional spin states becomes ground-states for Cr 3 (D 3h ) and CR 4 (T d ) respectively, indicating importance of GSO treatment of DFT for these clusters. Generalized spin orbital density functional theory multicenter metal clusters noncollinear molecular magnetism

For studying the group theoretical classification of the solutions of the density functional theory in relativistic framework, we propose quantum electrodynamical density-matrix functional theory (QED–DMFT). QED–DMFT gives the energy as a functional of a local one-body 4×4 matrix \documentclass{article}\pagestyle{empty}\begin{document}$Q(x)\equiv-\langle\psi(x)\bar{\psi}(x)\rangle$\end{document}, where \documentclass{article}\pagestyle{empty}\begin{document}$\psi$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$\bar{\psi}$\end{document} are a 4-component Dirac field and its Dirac conjugate, respectively. We examine some characters of QED–DMFT. After these preparations, by using Q(x), we classify the solutions of QED–DMFT under O(3) rotation, time reversal, and spatial inversion. The behavior of Q(x) under nonrelativistic and ultrarelativistic limits is also presented. Finally, we give plans for several extensions and applications of QED–DMFT. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002

No-overlap and orientation principles for ferromagnetic interactions between organic radicals were derived on the basis of approximately spin-projected UMP4(2) and UCC SD(T)/4-31G computations for several typical radical pairs. Ferromagnetic intermolecular interactions are feasible at T-shape and rhombus conformations in parallel interplane orientations for radical pairs because of no-overlap between π*-type SOMOs (no kinetic exchange) and nonzero-potential exchange via the SOMO-SOMO through-space contact, whereas antiferromagnetic kinetic exchange interactions are predominant at many other conformations.

Spin densities for nitronylnitroxide, phenyl nitronyl nitroxide(PNNO) and p-NPNN in the β-phase crystal were calculated by UHF, APUHF and UKS B(S)-LYP methods. Ab initio UHF overestimated a negative spin densitiy induced on the α-carbon atom of nitronylnitroxide group by spin polarization effect, whereas the approximately spin-projected UHF(APUHF)/6-31G* method provided a reasonable negative spin density on the α-carbon atom and almost equal distributions of the spin densities on nitrogen and oxygen atoms in PNNO and p-NPNN, in accord with the recent experiments. The spin populations on the benzene ring in these species by APUHF/6-31G* and APUHF/INDO, and UKS B-LYP/6-31G* methods were similar to the experimental values, indicating the important role of the spin polarization effect.

Herein, we have theoretically investigated the optical properties of the two Au8complexes with different shapes of the Au8cluster core. From the results of TD-DFT and DFT calculations, it was found that the shape of the Au8clusters in the two Au8complexes greatly influenced their optical properties, such as absorption and photoluminescence spectra. In particular, the intensities of their photoluminescence spectra are greatly decreased with an increase of the Au–Au bond length variation of the Au core cluster in the S1states of the Au8complexes.