Toward multiscale modelling: the role of atomistic simulations in the analysis of Si and SiC under hydrostatic compression

Abstract

The structural responses of silicon and silicon carbide under hydrostatic compression have been analyzed by using Tersoff interatomic potential function. We show the elastic stability criteria, based on the elastic stiffness coefficients gives consistent predictions of critical pressures at which the lattices become unstable with molecular dynamics simulations. However, the predicted values are considerably higher than that of another prediction based on the thermodynamic criteria. By calculating activation barriers for the homogeneous silicon phase transition from cubic diamond to β-Sn, we suggest that the elastic and thermodynamic criteria give upper and lower bounds respectively on the transition pressure. We also show that the effect of the atomic size disparity between Si and C atoms can be dominant in favoring amorphization over polymorphic transition in silicon carbide.