ABSTRACT
Energy eigenvalues and wave functions of hydrogen atoms in hydride LaNi(5)H(7) are calculated. First-principles electronic structure calculations are employed to obtain the three-dimensional potential energy structure of each hydrogen site. These quantum effects are not negligibly small in evaluation of enthalpy of formation, an important property of hydrogen storage. Including the temperature effect from hydrogen gas, experimental values are well reproduced. The excitation probability of inelastic neutron scattering is also calculated using the wave functions obtained.
ABSTRACT
In order to clarify the effect of hydrogen vacancies on the stability and structure of sodium alanate, NaAlH(4), with and without Ti substitution for Al, first-principles electronic structure calculations were carried out. The relative thermodynamic stability of the Ti dopant and the H vacancy in a supercell was obtained. For the Ti-doped Na(16)Al(16)H(64) supercell calculations, it was preferable to perform the initial substitution with a cluster of TiAlH(n). We showed that substitution of a Ti atom for an Al atom in Na(16)Al(15)TiH(63) with H vacancies increases the stability of the structure. A density of states analysis revealed weakening of the bond strength corresponding to increase in the bond length.
