ATOMIC-SCALE STRUCTURE AND ELECTRONIC-PROPERTIES OF HIGHLY TETRAHEDRAL HYDROGENATED AMORPHOUS-CARBON

The electronic band-gap properties of high-density, highly tetrahedral ly bonded, hydrogenated amorphous carbon are related to the size and o verlap distribution of small pi-bonded clusters embedded within a stra ined rigid sp(3) matrix of atomic-scale models generated by semiempiri cal density-functional molecular dynamics. Compared to the hydrogen-fr ee analogues of similar density and chemical composition, the residual strain in the network is reduced. As a consequence the overlap of p o rbitals between undercoordinated sites is enforced in favor of forming strong pi bonds, which is consistent with a further band-gap opening relative to the hydrogen-free structures.