A molecular dynamics study was made of self-diffusion in liquid Si and Ge, and of impurities in liquid Ge, by using empirical Stillinger-Weber potentials and several choices of parameters. A numerical algorithm was used in which the 3-body part of the Stillinger-Weber potential was decomposed into the product of 2-body potentials, thus permitting the study of large systems. One choice of Stillinger-Weber parameters was found to agree very well with the observed liquid Ge structure factors. The diffusion coefficients at the melting point were approximately 6.4 x 10-5cm2/s for Si, in good agreement with previous calculations, and 4.2 x 10-5 or 4.6 x 10-5cm2/s for 2 different models of Ge. In all cases, the diffusion coefficient could be fitted to an Arrhenius relationship, with activation energies of about 0.42eV for Si and 0.32 or 0.26eV for 2 different models of Ge; as calculated using either the Einstein relationship or a Green-Kubo type integration of the velocity auto-correlation function. The diffusivity of Si in liquid Ge was found to be very similar to the self-diffusion coefficient of liquid Ge.

W.Yu, Z.Q.Wang, D.Stroud: Physical Review B, 1996, 54[19], 13946-54