Localized electron states in the arsenic chalcogenides

In order to explain experimental observations on amorphous arsenic chalcogenides, it has recently been proposed that these compounds contain a high density of dangling bonds with rather special properties. However, chemical considerations raise doubts as to the plausibility of this model, which also does not readily account for the observed a.c. conductivity. An alternative model is proposed, in which the main localized states arise from bonding orbitals on arsenic-arsenic bonds and antibonding ones on chalcogenide—chalcogenide bonds. This model accounts well for a large range of experimental results for these compounds.