NMR Relaxation in Adamantane and Hexamethylenetetramine: Diffusion and Rotation

Abstract The ultraslow-motion NMR technique has been used to measure translational diffusion coefficients in the plastic crystal adamantane; The diffusion coefficients in the brittle crystal hexamethylenetetramine (HMT) were too low to be measured by this technique; they are smaller than those for adamantane by a factor of 10−4. It is claimed on the basis of Weertman's theory that this difference in diffusion coefficients accounts for the difference in plastic flow properties between the two materials. For rotation in β-adamantane, α-adamantane, and HMT the respective jump times are: