Atomistic thermodynamic calculations were made of the energetics of self-diffusion. An assessment of the activation enthalpy of the saddle-point configuration of various modes of vacancy self-diffusion indicated that second-nearest neighbor hopping was the most energetically favorable mechanism, if vacancies were available in equilibrium concentrations. An assessment of the activation entropy indicated that normal diffusion pre-exponential factors, of the order of 10-5 to 0.1cm2/s, were consistent with vacancy self-diffusion via second-nearest neighbor hopping. It was proposed that self-diffusion which was characterized by pre-exponential factors of the order of 107 to 108cm2/s, and activation energies of the order of 6eV, involved processes in which surface vacancy generation was inhibited and self-diffusion was mediated by Frenkel pair generation.

J.F.Wager: Journal of Applied Physics, 1991, 69[5], 3022-31