A STUDY ON SHORT-RANGE ORDER IN SOME ALLOYS OF THE CU-AS-SE GLASSY SYSTEM BY X-RAY RADIAL-DISTRIBUTION ANALYSIS

The radial atomic distribution was studied in the amorphous alloys Cu(x)As0.5-(x)Se0.5, with x = 0.05 (MI), x = 0.10 (MII) and x = 0.20 (MIII), using X-ray diffraction data of samples of these alloys obtained by quenching the molten material. The short-range order proposed was determined through the interpretation of the radial distribution function (RDF), using a theoretical expression which takes into account the variation in the atomic dispersion factors with s (scattering vector module) and approximating them to polynomic functions. Different coordination hypotheses for Cu, quoted in the literature on glassy alloys containing this element, were taken into account. The result of the study is that tetracoordinated Cu is the hypothesis which best agrees with the experimentally-obtained structural information, so the most probable short-range order for the Cu-As-Se system alloys studied is made up of tetrahedral units centred on interlaced copper and arsenic atoms, forming a network.