Tight-binding molecular-dynamics simulations of amorphous silicon carbides

Atomic and electronic structures of amorphous tetrahedral silicon carbide a-SiC are analyzed on the basis of molecular dynamics simulations performed in the framework of a sp(3)s(*) tight-binding force model. The a-SiC samples are generated from dilute vapors and melts. The topology and the local chemical order of the resulting amorphous networks are very sensitive to the initial high-temperature structures. The simulations are used to investigate the electronic distribution in the band gap region and the changes in the density of states caused by the presence of homo-polar bonds, coordination defects, and strongly distorted tetrahedral species. For completeness the results obtained for a-SiC are compared with those from various semiempirical schemes and from ab initio pseudopotential calculations.