Insight into crystalline, electronic, and mechanical characteristics of calcium sulfate minerals based on density functional theory

DFT was chosen to examine the crystalline, electronic, and mechanical characteristics of CaSO 4 •nH 2 O (n = 0, 0.5, and 2). There is excellent agreement between the estimated lattice parameters of those calcium sulfate mineral crystals and the available experimental data. All calcium sulfate minerals share the same structural motifs, including CaO 8 polyhedra and SO 4 tetrahedral groups. Because of their identical structural units, the O-2s, S-3p, and Ca-3d orbitals were mostly influenced by the electronic characteristics of those calcium sulfate minerals. The density of states (DOS) for all calcium sulfate minerals exhibits pronounced molecular-like characteristics, featuring highly localized peaks. While the H 2 O molecules in gypsum and hemihydrate are equivalent, their geometry in these hydrated minerals is significantly distorted compared to free H 2 O molecules. The computed single-crystalline elastic constants are used to determine the anisotropy factor, bulk modulus, shear modulus, Poisson’s ratio, Young’s modulus, and Lame’s coefficient, providing significant insights into the mechanical characteristics of certain calcium sulfate minerals. According to the B/G ratio study, anhydrite behaves ductilely, while hemihydrate and gypsum display brittle behavior. The degree of elastic anisotropy follows the order: anhydrite > gypsum > hemihydrate. A thorough comprehension of these minerals’ characteristics will be crucial for the practical application of calcium sulfate-based materials.