First-principles investigations of transition metal dihydrides, TH2 : T = Sc, Ti, V, Y, Zr, Nb; energetics and chemical bonding

Self-consistent full-potential linearized augmented-plane-wave (LAPW) band- structure calculations are performed for the fluorite-type dihydrides ScH2, TiH2, VH2, YH2, ZrH2 and NbH2 as well as for the tetragonal low-temperatur e phases of TiH2 and ZrH2. For all compounds studied which show metallic be haviour, band structures, densities of states, electron densities and the t otal-energy minima with respect to the lattice parameters are computed. Add itionally, the bulk moduli for the cubic phases are given. Good agreement w ith experimental data is found where they are available. The results obtain ed confirm previous interpretations of the tetragonal distortion of the cub ic unit cell as a Jahn-Teller-type effect and show how the electron densiti es of the tetragonally distorted phases depend on the splitting of states n ear the Fermi level. The total-energy curves for TiH2 and ZrH2 as functions of the cia ratios show two minima each, of which only the ones for c/a < 1 have been observed experimentally.