Ab Initio Simulations of Liquid and Amorphous SiC and SiCN

摘要

We carried out ab initio molecular dynamics simulations of amorphous and liquid silicon carbide (1-SiC, a-SiC) and silicon carbon nitride (1-SiCN, a-SiCN). In the liquid phases, the tendency of carbon towards low coordination dominates the structural characteristics. Silicon coordination in both liquids is comparable with that in pure 1-Si. It is found that the network of the amorphous phases deviates from an ideal tetrahedral geometry because a considerable number of C atoms are threefold coordinated. Silicon atoms are slightly over-coordinated in both the samples. In a-SiCN the Si network are strongly distorted and no preference for tetrahedral coordination. In contrast to a-SiC, in the amorphous Si-C-N system, the Si-Si nearest neighbour correlations are weakly shown. Our simulation is in good agreement with most measurements.