Abstract
Silicon disulfide, , is thought to occur in interstellar dust and is of fundamental interest more generally among the silicon chalcogenides as a comparator to , an important component of terrestrial planets. However, the high-pressure behaviors of silicon sulfides are unclear. Here, using an efficient structure search method, we systematically explore the structural evolution of different Si-S stoichiometries up to 250 GPa. is found to be stable below 155 GPa, above which it decomposes into two compounds, SiS and . SiS adopts a high-symmetry cubic structure consisting of eightfold-coordinated silicon in face-sharing polyhedra, while crystallizes in a rhombohedral structure containing ninefold-coordinated polyhedra. Analyses suggest that the Si eightfold-coordination environment could be a common feature for group IV–VI compounds under high pressure. Our findings provide insights on the nature of Si-S compounds under ultrahigh pressure.
- Received 31 January 2019
- Revised 24 April 2019
DOI:https://doi.org/10.1103/PhysRevB.99.184106
©2019 American Physical Society