Theory of Light Interstitials in BCC Metals. II. Localized Vibration Spectra of H and D on T-Sites in V, Nb and Ta

The energy and wave functions of the ground and excited states have been calculated for hydrogen isotopes (H and D) self-trapped on the tetrahedral (T) site in bcc metals V, Nb and Ta. Results of the calculation account well for all features of localized vibration spectra observed by inelastic neutron scattering, including the excitation energy and the relative intensity of peaks. In addition, it has been shown that the excitation energy varies sensitively with displacements of surrounding metal atoms, leading to the interpretation that the observed broadening of the peaks is caused by lattice deformation arising from lattice vibration and the presence of other H (D)-atoms.