Quasi-elastic neutron scattering experiments were carried out on the high-temperature α-phase of 7Li2SO4, with the aim of elucidating anion and cation dynamics and their possible correlation (paddle-wheel mechanism), since this material was the most important example of a fast-cation conducting plastic phase. When Q was less than 0.12nm, the quasi-elastic linewidth varied as DQ2, where D was the Li tracer diffusion coefficient. At higher Q-values, a wave-like structure was found; with linewidth maxima at 0.14 and 0.25nm and a minimum at 0.19nm. This behaviour was typical of coherent diffusion (7Li scattered both coherently and incoherently). At higher Q-values, there was a (coherent) quasi-elastic contribution which arose from the O nuclei; due to anion reorientation.

Cation and Anion Dynamics in the Fast-Ion Conducting Rotor Phase of 7Li2SO4. D.Wilmer, H.Feldmann, R.E.Lechner: Physica B, 2000, 276-278, 232-3