Molecular-Orbital Studies of As2S3 and As2Se3

Abstract

The basis hybrid orbitals of ${\mathrm{As}}_2$ ${\mathrm{S}}_3$ and ${\mathrm{As}}_2$ ${\mathrm{Se}}_3$ for the molecular-orbital calculation of the layer molecules have been investigated. One feature distinct from and one similar to amorphous Se is observed. The former is the inequivalence of the nearest-neighbor $\sigma$ bonds, which can be interpreted as a reason for low carrier mobilities in these solids. The similar feature is the locations of the bonding and the lone-pair states. As in Se, these are intermixed; thus band-gap photons can break $\sigma$ bonds, which accounts for the photodissociation and photocrystallization of chalcogenide glasses.