Short- and medium-range order in Sb–Se glasses

Abstract

Neutron diffraction measurements were performed to investigate the structure of SbxSe100−x bulk glasses with x=5, 10, 15, 20 and 25at% Sb. The total pair distribution functions show two peaks at 2.36Å and 2.64Å, which are attributed to Se–Se and Sb–Se bonds, respectively. The coordination numbers calculated from these peaks indicate that Sb atoms are three-coordinated and Se atoms are two-coordinated for all the above compositions. However, the composition dependences of the first two peaks in the structure factors show an obvious change between 15 and 20at% Sb, indicating that the medium-range structure is changed in this range of Sb content. In order to elucidate the medium-range structure, reverse Monte Carlo simulation was used with coordination number constraints. The structure models consisting of a mixture of the SbSe3/2 network and Sen chain clusters were in good agreement with neutron diffraction data for Se-rich glass (5, 10 and 15at% Sb). On the other hand, a better fit was obtained for Sb25Se75 glass with a model based on the network structure formed by connected SbSe3 units.