Expressions for the calculation of the parameters of self-diffusion in a crystal of simple substance at temperatures close to absolute zero were derived. It was established that, in so-called loose crystal structures (with a first coordination number below 12), the number of atoms involved in diffusion motion exceeded the number of vacant sites in the crystal lattice at 0K. The results of calculations of the vacancy and diffusion parameters at 0K for 10 cryocrystals showed that the phenomenon of so-called non-vacancy self-diffusion at 0K could take place only in body-centered cubic He.

On the Role of Vacancies in the Process of Self-Diffusion at Low Temperatures. M.N.Magomedov: Technical Physics Letters, 2002, 28[5], 430-3