ELECTRONIC-STRUCTURE AND CHEMICAL-BOND IN STOICHIOMETRIC HYDRIDES OF THE GROUP-VB METALS

The electronic structure of stoichiometric hydrides of the group Vb me tals (V, Nb, Ta) has been investigated by means of the self-consistent full potential scalar-relativistic augmented plane wave method (FP-AP W). The theoretical study of the heat of solution of the ordered monoh ydrides VH, NbH, and TaH leads to good agreement with experimental val ues and allows the prediction of the preferred coordination of the hyd rogen atoms in these phases, i.e. the octahedral coordination for the VH-system and the tetrahedral coordination for NbH and TaH. Analysis o f the charge distribution according to the irreducible representations of the point groups yields a simple orbital picture of the bonding me chanism in the stoichiometric hydride phases. The use of an angular-de pendent rather than a spherical-symmetric potential results in a disti nct increase in the calculated covalent contribution to the chemical b ond.