Theory of electronic states in disordered alloy hydrides

Band structure calculations of metal hydrides have provided understanding of the bonding characteristics of these materials and clarified the mechanisms involved in various physical properties such as superconductivity. Since the electronic structure of stoichiometric hydrides has been discussed extensively in the literature, in this article we will focus on the methodology and results of disordered hydrides. This disorder can occur on the metal site of the hydride by considering random substitutions of the host metal or on the hydrogen sublattice where vacancies appear. The theory that we use is based on the coherent potential approximation and proceeds as follows. Self-consistent band structure calculations of typical metal hydrides are performed by the augmented plane wave method. The results of these calculations are fitted to a tight-binding Hamiltonian using a Slater-Koster type of procedure. This Hamiltonian is then used in a tight-binding version of the coherent potential approximation which gives us the electronic densities of states for different metal and hydrogen compositions