Structural models of amorphous GeS

Abstract

We have constructed two hand-built CRN structural models of a-GeS. We have assumed 4:2 coordination for the Ge and S atoms respectively, and allowed only Ge—S and Ge—Ge bonds. The models contain 430 and 350 atoms. They differ both by the statistics of the tetrahedra Ge(Ge_4-nS_n) and by their medium-range order. The first model corresponds to a three-dimensional network with random statistics for the tetrahedra, the second one represents a layered structure built mainly of Ge(Ge₂S₂) units. The models were relaxed with respect to the Keating potential. We have observed the existence of close pairs of non-bonded sulphur atoms. Therefore we also had to include suitable repulsion forces into the relaxation procedure. Comparison of the calculated and observed structural characteristics, density and radial distribution function (RDF), showed that the structure of a-GeS may be represented by the three-dimensional CRN, but not by the layered model.