Investigation of the electronic structure and phonon anharmonicity inβ- andγ-NbH

First-principles electronic-structure and total-energy calculations have been performed for NbH in the {β}- and {γ}-phase structures. Lattice constants, bulk moduli, and heats of formation have been calculated and found to be in excellent agreement with measured values. We have made detailed ``frozen-phonon'' calculations investigating the effect of anharmonic couplings on the optical vibrations of hydrogen and its isotopes in NbH.