The effect of ionic diffusion on Li spin–lattice relaxation in Li2Si4O9 glass was studied by using the molecular dynamics simulation technique at 2000 to 3800K. The orientational pair correlation function G(t) associated with spin–lattice relaxation was computed for individual Li ions from the trajectories of the constituent ions at different temperatures. The temporal decay of G(t) was found to be non-exponential and could be described by the stretched-exponential functional form exp(-t/τSLR)ρ. It was shown that the non-exponential behavior of G(t) was intrinsic to the system, possibly originating from hierarchically constrained relaxation processes. The activation energies associated with Li diffusion, τSLR and the average conductivity relaxation time <τσ> were shown to be in excellent agreement indicating that the same microscopic dynamic processes were responsible for spin–lattice relaxation, diffusion and conductivity. However, τSLR was found to be nearly an order of magnitude longer than <τσ> over the entire temperature range of these simulations. This result reflects the fundamental differences between the correlation functions associated with spin–lattice relaxation and conductivity relaxation. The existing experimental data in the literature on spin–lattice relaxation in normal and fast-ion conducting glasses were shown to be completely consistent with the results obtained from the present simulations.

A Molecular Dynamics Simulation Study of Ionic Diffusion and NMR Spin–Lattice Relaxation in Li2Si4O9 Glass. S.Sen, T.Mukerji: Journal of Non-Crystalline Solids, 2001, 293-295, 268-78