Calcium zinc oxysulfide: Newfound polytypes for potential optoelectronic applications

CaZnOS has attracted significant scientific interest, particularly for its layered structure, advanced properties, outstanding doping ability, and structure–property relationships. The CaZnOS compound was synthesized through high-temperature experiments and characterized by X-ray powder diffraction (XRPD). The crystal structure of CaZnOS exhibits noncentrosymmetric hexagonal symmetry with the space group P6₃mc. The spectra of possible CaZnOS polytypes were investigated, predicting structural configurations that differ from those previously proposed or observed in CaZnOS, encompassing bulk crystal forms, nanostructures, or junction-based architectures. All computations were conducted using first-principles density functional theory (DFT) and five different functionals (local density approximation (LDA)–Perdew–Zunger (PZ), generalized gradient approximation (GGA)–Perdew–Burke–Ernzerhof (PBE), Becke three-parameter Lee–Yang–Parr (B3LYP), parameter-free Perdew-Burke-Ernzerhof (PBE0), and Heyd–Scuseria–Ernzerhof (HSE06)). Recently developed algorithms were used for structure prediction, and the predicted CaZnOS polytypes were investigated for their stability and electronic and vibrational properties. Consequently, numerous potential stable and metastable CaZnOS polytypes were identified, opening new possibilities for the synthesis of innovative materials with improved properties.