Modeling the structure and photostructural changes in amorphous arsenic sulfide

Abstract

Models of the atomic structure and the photostructural changes of amorphous arsenic sulfide, a-As 2 S 3 , are discussed and compared with experiment. It is shown that structural units involving two coupled AsS 3 pyramids surrounding a shared S atom provide elements of intermediate range order, IRO, sufficient to describe available data. These elements are shown to be configured such that the dihedral angle relationships defined by the two bonds of the shared S-atom make helical and bridging S-atom sites identifiable. Reversible photostructural changes are modeled in terms of these units.