Molecular dynamics calculations of defect energetics in β-SiC

Abstract

The molecular dynamics (MD) method is used to calculate defect energetics in β-silicon carbide. Many-body interaction effects in this covalent material are accounted for by using a hybrid of two-body and three-body potentials. Pearson's potential is modified to accurately fit the sublimation energy of β-SiC, and interatomic potentials among silicon, carbon, and helium atoms are also developed. A microcrystal is constructed to represent the computational cell, and external forces are applied to its boundaries so that it behaves as a part of an infinite medium. The potential energy for the unperturbed computational cell is first calculated. The cell is then set at a chosen defect configuration and relaxed, and the potential energy of the relaxed cell is computed. The difference between the potential energies of the unperturbed cell and that of the defect-containing cell is used to calculate the formation energies of point defects and defect clusters in SiC. Binding energies, and migration energies of point defects are then deduced. Preexponential factors of point defect diffusion coefficients are derived from the calculated potential energy profile. Activation energies and preexponential factors of thermal diffusion through the vacancy mechanism are compared to corresponding experimental data.