Topological modeling of amorphization in SiC nodal network structures using local rules

Local rules, with the nodes instead of traditional tetrahedrons as the basic elements, are developed for the self-assembly of SiC networks. In our models, amorphous alpha- and beta-SiC networks are generated by considering two factors: deviant rules based on the modifications of the corresponding crystalline assembly rules and chemical disorders caused by the anti-site defects. In the deviant rules, to substantially capture the mechanical configurations, springs are applied to the assembly process. Using the matrices of rotation and nodal coordinates to generate crystalline and amorphous assemblages alike, we can readily obtain the density, local clusters, dihedral-angle distributions and pair distribution functions. In addition, the anti-site defects are introduced into the assembly process, with the assembly defect density as a controllable parameter to investigate its effect on the structure evolution. The results show that the homonuclear ratio below 0.01 resulting from the low defect density does not lead to significant topology disorder; while the higher defect accumulation affects topology disorders and causes the structures to become completely amorphous. By comparing with molecular dynamics simulations and experiments, it is demonstrated that the reasonable amorphous SiC structures could be generated by deviant rules in combination with the imposition of chemical disorder. (C) 2011 Elsevier B.V. All rights reserved.