Neutron quasi-elastic scattering measurements were performed, on powdered samples of crystalline intermetallic phase with a H/metal ratio of 1:6, at momentum transfers of from 4 to about 20/nm and temperatures of 400 to 460K. It was found that about 80% of the spectral area could be accounted for by a Lorentzian function with an energy half-width of 1 to 10eV; depending upon the momentum transfer and temperature. The addition of a further Lorentzian function, with a half-width of about an order of magnitude less, was required in order to give the true shape of the spectrum. The temperature dependence of the spectral width was consistent with activation energies of 0.32 and 0.395eV. The relationship between the quasi-elastic spectrum and H diffusion was explained in terms of the hopping rates and jump lengths which were deduced from nuclear magnetic relaxation measurements and the structural properties of the alloy. This alloy was of particular interest because amorphous Ni-Zr alloys could also form near to this composition. In spite of the similarities in the distribution of metal atoms around the sites that were occupied by H, the diffusion properties of the amorphous alloys (as deduced from previous quasi-elastic measurements) were very different.

M.Asif, R.L.Havill, J.M.Titman, B.Frick: Journal of Alloys and Compounds, 1995, 231, 243-7