Medium-range structural changes in glassy As2S3 driven by high-energy mechanical milling

Abstract

Effect of high-energy dry mechanical milling on medium-range order structure in glassy arsenic sulfide g-As2S3 was studied employing the X-ray powder diffraction (XRPD) analysis. The results were treated in terms of model assuming appearance of diffuse halo in the XRPD patterns of g-As2S3 known as the FSDP (the first sharp diffraction peak) due to remnants of inter-planar quasi-crystalline correlations with Bragg diffraction spacing approaching ~5.1 Å, supplemented by the post-FSDP halo at ~1.5 Å−1 originated from inter-atomic cation-cation correlations. Thermodynamically stabilized balance in network-forming entities in glass structure was shown to be essentially disturbed under milling, providing an evidence on a variety of defective states with unfavorable potential energies. The inter-planar correlations contributing to the FSDP were essentially disturbed under milling making the correlated distances between atomic pairs belonging to neighboring planes more prominent, like it was detected in chalcogenide glasses under applied hydrostatic pressure. The impact of milling-driven fragmentation on the correlation lengths of quasi-crystalline remnants was confirmed by slight decrease in the FSDP position and, in contrast, noticeable broadening in its width. The non-elementary nature of this peak-halo due to post-FSDP hump became more prominent after high-energy milling. Comparative study of milling-derived g-As45S55 and As50S50 mechanically treated under similar conditions confirmed unique compositional FSDP parameterization in binary g-As-S system.