Magnetization recoveries for nuclear spin relaxation of like spins due to magnetic dipolar coupling and diffusion on inequivalent sites involve a sum of exponentials. The theory was applied to diffusion on octahedral and tetrahedral interstitial sites in the face-centered cubic structure. Monte Carlo simulations were used to generate relaxation data for parameters typical for H in metals. It was found that only a single exponential would be observable in the high- and low-temperature limits, but that two-exponential recoveries could be observable in the vicinity of the maximum in the relaxation rate as a function of temperature. The Monte Carlo relaxation data was fitted using a Bloembergen-Pound-Purcell model to assess the accuracy of the latter mode.

Nuclear Spin Relaxation Due to Motion on Inequivalent Sites: H Diffusion on O and T Sites in the Face-Centred Cubic Structure. X.Luo, C.A.Sholl: Journal of Physics - Condensed Matter, 2003, 15[6], 937-44