Band modes of hydrogen in the bcc metals Nb, V, and Ta

A calculation of the frequency spectrum of the band modes of hydrogen located at a tetrahedral interstitial site shows a strong resonantlike peak with very little isotope effect. This mode was observed by neutron scattering in Nb${\mathrm{H}}_{0.05}$ at 3.8 THz. The band modes provide a mechanism for classical diffusion with low activation energies.