Predicted Binary Compounds of Tin and Sulfur

Three known binary compounds of tin (Sn) and sulfur (S), namely, SnS, SnS₂, and Sn₂S₃, have been extensively studied for potential application in energy generation and conversion applications. Inspired by the existence of many metastable phases of SnS, we explore the chemical space of nine crystalline solids with chemical composition Sn_<i>x</i>S_1–<i>x</i> (<i>x</i> falls between 0.25 and 0.75), predicting that Sn₃S is thermodynamically stable in a metallic <i>Pmn</i>2₁ phase. Due to the layered structure of this phase, Sn₃S is a quasi two-dimensional material, characterized by highly anisotropic electronic-related properties. Moreover, the discovered metastable structures of Sn₃S₂, Sn₂S, and Sn₅S₂ are just about 5 meV/atom above the stability limit, and may potentially be realized. The data set of 369 low-energy structures of nine Sn_<i>x</i>S_1–<i>x</i> crystalline solids reported in this work is a reliable sample of the low-energy sector of the chemical space, and thus being useful for the currently established materials databases, providing a playground for future data-mining works in materials discoveries