Variation of the parameters of self-diffusion in a crystal of simple substance caused by changes in the isotope composition were theoretically studied in the regions of high and low temperatures. The results of numerical calculations performed for diamond and bcc lithium crystals were presented. It was shown that the isotope dependence of the self-diffusion coefficient D was weak at high temperatures but became substantial at low temperatures: at T = 0, the D value increased by an order of magnitude on the passage from 7Li to 6Li and decreased by three orders of magnitude on the passage from 12C to 13C. This isotope effect was related to the phenomena of quantum tunneling and zero-point oscillations of atoms in crystals at T = 0. The isotope dependence of the interatomic interaction potential significantly influenced the self-diffusion coefficient only at high temperatures.

Variation of the Coefficient of Self-Diffusion in a Crystal Caused by Changes in the Isotope Composition. M.N.Magomedov: Technical Physics Letters, 2006, 32[5], 434-8