Self-Diffusion in Solid Argon

The self-diffusion coefficient D=D₀exp(-Q⁰RT) for solid argon has been measured in thin specimens of large grain size by a tracer technique. The results, D₀=0.2±0.140.35 cm² sec^-1 and Q⁰=3600±150 cal mole^-1, are lower than those obtained in previous investigations. The value of Q⁰ agrees reasonably well with a two-body absolute-rate calculation for vacancy migration, but not with calculations based on divacancy or interstitial mechanisms. The results suggest that vacancy diffusion takes place, and that many-body forces in solid argon are either very small, or else may satisfactorily be accounted for in an empirical two-body potential.