Calculated Isotope Effect for Diffusion in Solid Argon

The isotope effect was calculated for diffusion in solid argon using a formalism developed by Glyde. The computed values of ΔK are 0.99 for self-diffusion via a single-vacancy mechanism, 0.88 for self-diffusion via a divacancy mechanism, 0.999 for neon impurity diffusion via single vacancies, and 0.94 for krypton impurity diffusion via single vacancies. These calculated values are compared with experimental data and suggest that diffusion in solid argon may be via either a single-vacancy or divacancy mechanism; neither the calculations nor the experiments are sufficiently precise to establish the mechanism with certainty.