Short- and intermediate-range structural correlations in amorphous silicon carbide: A molecular dynamics study

Short- and intermediate-range structural correlations in amorphous silicon carbide (a-SiC) are studied in terms of partial pair distributions, bond angle distribution functions, and shortest-path ring statistics. A well relaxed sample is prepared following a slow annealing schedule of the simulation at the experimental density of the amorphous phase. The short-range correlation functions indicate a locally ordered amorphous structure with heteronuclear bonds, Si--C, with no phase separation, and no graphitic or diamond structures present. The bond distances and coordination numbers are similar to those in the crystalline phase. The rings statistics indicate an intermediate-range topology formed by the rearrangement of tetrahedra with the occurrence of corner and edge sharing units connecting two- (~5% of total), three-, four-, and five-fold rings. The presence of large size rings indicates the existence of nano-voids in the structure, which explains the low density compared with the crystal phase while keeping the same coordination number and bond distance. These simulation results agree well with experimental results.