Prediction of A2BX4 Metal-Chalcogenide Compounds via First-Principles Thermodynamics

Current compilations of previously documented inorganic compounds reveal a significant number of materials that are not listed. Focusing on the A ₂BX ₄ metal-chalcogenide group with A and B atoms being either main group elements or only one of them being a 3d transition metal, a total of 255 are reported, whereas 429 chemically reasonable A ₂BX ₄ are unreported. We have applied first-principles thermodynamics based on density functional methodology, predicting that about 100 of the 429 unreported A ₂BX ₄ metal-chalcogenides are likely to be stable. These include 14 oxides, 34 sulfides, 28 selenides, and 24 tellurides that are predicted here to be energetically stable with respect to decomposition into any combination of elemental, binary, and ternary competing phases. We provide the lowest-energy crystal structures of the predicted A ₂BX ₄ compounds, as well as the next few energetically higher metastable structures. Such predictions are carried out via direct first-principles calculations of candidate structure types and confirmed for a few compounds using the global space-group optimization (GSGO) search method. In some cases, uncommon oxidation states and/or coordination environments are found for elements in the stable A ₂BX ₄ compounds predicted here. We estimated the growth conditions in terms of temperature and partial pressure of the reactants from extensive thermodynamic stability analysis, and found dozens of compounds that might be grown at normal synthesis conditions. Attempts at synthesis of the stable A ₂BX ₄ compounds predicted here are called for.