Compositionally-dependent structural variations in glassy chalcogenides: The case of binary As[sbnd]Se system

Abstract

Structural peculiarities of glass formation in binary AsSe system occur to be compositionally dependent demonstrating anomalous oscillating tendencies toward intrinsic decomposition around some points within glass-forming region covering the range of Se-rich glasses. By employing ab-initio quantum chemical modeling with RHF/6-311G∗ basis set, known also as CINCA (the cation-interlinking network cluster approach), the geometrically-optimized configurations and mean forming energies were computed for different atomic configurations of As2Sem clusters (m=3–8). In respect to these calculations, the most essential instability is expected in AsSe glasses near average atomic coordination of Z=2.25, where both local chemical and global phase-separation decompositions are favorable, while in a vicinity of Z=2.33, these glasses demonstrate only ability to local decomposition on As- and Se-rich network-forming structural fragments. These results explain well known compositional changes in physical properties of AsSe glasses caused by technology variations and prolonged physical aging.