Theoretical studies of grain boundaries in covalent materials

Abstract

Atomic and electronic structures of grain boundaries in covalent materials such as semiconductors or covalent ceramics have been investigated using various theoretical methods. Significant advances have been made in the understanding of grain boundaries in elemental semiconductors. Currently, ab initio calculations for grain boundaries are possible by virtue of the development of the first-principles molecular dynamics method. A first ab initio approach to grain boundaries in SiC by using the models of the {122} Σ = 9 boundary is presented. It has been shown that interfacial C-C and Si-Si wrong bonds have significant effects on grain boundaries in SiC. The C-C and Si-Si bonds have bond lengths and bond charges similar to those in bulk diamond and Si, and the C-C bonds generate peculiar localized states at the valence-band edges.