Structural models of the amorphous alloy ${\mathrm{Ge}}_{0.20}$${\mathrm{As}}_{0.40}$${\mathrm{Se}}_{0.40}$ by a random technique

Three different spherical-shaped models of the amorphous alloy ${\mathrm{Ge}}_{0.20}$ ${\mathrm{As}}_{0.40}$ ${\mathrm{Se}}_{0.40}$ , obtained from quenching of the molten mixture of the elements, were constructed. The models were built by computer simulation of an x-ray diffraction experiment. Initial models were created on the basis of the short-range order proposed from the radial distribution function (RDF) interpretation, consistent with the covalent coordination of the forming elements. The refinement has been carried out by the Metropolis Monte Carlo method with some modifications. A two-phase structure, consisting of cross-linked clusters of distorted tetrahedra centered on Ge atoms and structurally independent Se chains, has been considered the most probable. These clusters are linked to each other by means of chains of As and Se atoms. An analysis of its main structural parameters has been achieved. We propose the existence of a certain medium-range order, indicated by the appearance of a first sharp diffraction peak (FSDP) in the experimental interference function. This FSDP is reproduced in the theoretical interference function, calculated from the RDF of the proposed model.