Predicted semiconducting beryllium sulfides in 3D and 2D configurations: Insights from first-principles calculations

Light-metal sulfides have attracted great attention due to the technological application as energy storage devices. Combining first-principles calculations with structure searching, sulfur-rich compounds were explored theoretically in Be-S system. Interestingly, our results identify a hitherto unknown stoichiometry BeS2 in bulk and two-dimensional (2D) configuration. With the pressure increasing, BeS2 in bulk adopts P (1) over bar structure at ambient pressure, C2 phase over 1.6 GPa and then a cubic c-BeS2 with unique S-2(2-) dimmers up to 5.8 GPa. The monolayer penta-BeS2 with Be2S3 pentagons and bilayer BeS structure are presented. Predicted c-BeS2, 2D BeS2 and BeS phases show a semiconducting character, interestingly, cBeS(2) is found to have a direct band gap of 1.52eV. The discovery of unknown beryllium sulfides and the understanding of electronic and chemical bonding properties will provide prerequisite for the potential application in electrochemistry. (C) 2018 Elsevier B.V. All rights reserved.