Tamio Ikeshoji

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Size- and temperature-dependent structural transitions in gold nanoparticles were revealed with morphology statistics obtained by high-resolution electron microscopic observations for thousands of particles annealed in a helium heat bath. We found that gold nanoparticles over a wide size range, 3-14 nm, undergo a structural transformation from icosahedral(More)
We present a first-principles molecular dynamics study of water near and above the critical point ( T = 647 K, rho = 0.32 g/cm(3)). We find that the systems undergo fast dynamics with continuous formation and breaking of H bonds. At low density, the system fragments mostly into trimers, dimers, and single molecules. At a higher density, more complex(More)
The microscopic pressure tensor, which is not uniquely defined, is analyzed for a uniform hard-sphere fluid in Cartesian and spherical coordinates. Two popular definitions, one due to Irving and Kirkwood (IK) [J. H. Irving and J. G. Kirkwood, J. Chem. Phys. 18, 817 (1950)] and the other due to Harasima (H) [A. Harasima, Adv. Chem. Phys. 1, 203 (1958)], were(More)
The properties of aqueous sulfuric acid have been studied employing density functional theory-based molecular dynamics simulations in conjunction with norm-conserving pseudopotentials. The simulations were carried out for two different concentrations whose molar concentrations were fixed at 0.84 and 10.2 mol/l. The structural features of aqueous sulfuric(More)
A first principles study of a hydrated electron in water at ordinary and supercritical conditions is presented. In the first case, the electron cleaves a cavity in the hydrogen bond network in which six H2O molecules form the solvation shell. The electron distribution assumes an ellipsoidal shape, and the agreement of the computed and the experimental(More)
The ionic conduction and electrochemical and thermal stabilities of the LiBH4-LiCl solid-state electrolyte were investigated for use in bulk-type all-solid-state lithium-sulfur batteries. The LiBH4-LiCl solid-state electrolyte exhibiting a lithium ionic conductivity of [Formula: see text] at 373 K, forms a reversible interface with a lithium metal electrode(More)
First-principles molecular dynamics simulations have been carried out to investigate the nature of proton dynamics in Nafion, a representative polymer electrolyte membrane (PEM) widely used in PEM fuel cells. From the trajectories of the simulations, diffusion coefficients for the protonic defects were calculated to be 0.3 x 10(-5) cm(2) s(-1) and 7.1 x(More)
Despite many exploratory studies over the past several decades, the presently known transition metals that form homoleptic transition-metal hydride complexes are limited to the Groups 7-12. Here we present evidence for the formation of Mg3 CrH8 , containing the first Group 6 hydride complex [CrH7 ](5-) . Our theoretical calculations reveal that(More)
The effects of water content on water transport and electro-osmosis in a representative polymer electrolyte membrane, Nafion, are investigated in detail by means of first-principles molecular dynamics (MD) simulations in the presence of a homogeneous electric field. We have directly evaluated electro-osmotic drag coefficients (the number of water molecules(More)