A molecular dynamics study was made of self-diffusion on the basis of volume-dependent pair potentials that were constructed using second-order pseudopotential perturbation theory. It was shown that the migration energy of monovacancies, as deduced from mean-square displacements, agreed well with the migration energy which was predicted by transition-state theory. It was concluded that the contribution, which was due to the appearance of Frenkel pairs in thermal equilibrium at high temperatures, to self-diffusion was characterized by distinctly higher pre-exponential factors and higher activation energies than that due to vacancies. It was noted that it could therefore be easily recognized if it became significant well below the melting point.

Molecular-Dynamics Study of Self-Diffusion in Na: Validity of Transition-State Theory V.Schott, M.Fähnle, A.Seeger: Physical Review B, 1997, 56[13], 7771-4