By using molecular dynamics methods, and the activation-relaxation technique, an investigation was made of the inherent structure and diffusion properties of the liquid. With increasing density, the 52 and 60º peaks (attributed to long bonds) in the bond-angle distribution functions decreased in height. Meanwhile, the main peak, which was mainly related to bonds with some covalent character, increased and moved towards the tetrahedral angle. The change in density did not give rise to a clear change in the diffusion constants. With changes in temperature, the diffusion coefficients which were deduced from the average mean square displacement could be fitted using the Arrhenius equation:

D (cm2/s) = 3.08 x 10-2 exp[-0.92(eV)/kT]

However, the activation energy which was deduced by using the activation-relaxation technique, with a Metropolis accept-reject criterion and a fictitious temperature of 0.5eV, ranged from 0.22 to 1.0eV. It also exhibited a steep increase at low temperature. The very large pre-exponential factor suggested that the interatomic forces which resulted from the Tersoff potential were very strong. These predictions were consistent, to some extent, with experimental results for liquid Si.

Molecular-Dynamics Simulation of the Structure and Diffusion Properties of Liquid Silicon Z.G.Zhu, C.S.Liu: Physical Review B, 2000, 61[14], 9322-6

Table 24

Diffusivity of Sb and Sn in Si at 1000C in Various Ambients

and with Various Sb and/or Sn Distributions in the Sample