The Vacancy Concentration and Diffusion in Rare Gas Solids H

Using the two-body Mie, Lennard-Jones potentials derived from solid state properties, the vacancy concentration p. and self-diffusion coefficient D are calculated for the rare gas solids. The results are summarised in Tables l-3. Agreement is obtained with the observed D but not with p.. If the usual interpretation is applied, the agreement of I) suggests the absence of many-body forces whereas the disagreement of pv suggests a contribution of 20 per cent. It is argued generally (Section 4~) that at best only indirect, and perhaps misleading, evidence on many-body forces is obtained from the study of these properties. if a comparison with other solids is meaningful, it appears that either the recent data on p,, and D are conflicting or diffusion is not via the usual vacancy mechanism, the latter seeming less likely at present.