Influence of the electronic structure on the titanium-vanadium-hydrogen phase diagram

Calculations have been carried out for cubic TiH2 and VH2 and the tetragonally-distorted TiH2 in an attempt to explain the phase diagram of the Ti-V-H system. The calculations demonstrate that the distortion is caused by the existence of degenerate states at the Fermi level, degeneracy of which is lifted by the tetragonal distortion - an example of the Jahn-Teller effect in a metal. The effect of varying vanadium concentration and varying hydrogen concentration on the position of the phase boundaries is discussed in terms of the calculated results. (Auth.)