Modeling the Ternary Chalcogenide Na2MoSe4 from First-Principles

In the ongoing pursuit of inorganic compounds suitable for solid-state devices, transition metal chalcogenides have received heightened attention due to their physical and chemical properties. Recently, alkali-ion transition metal chalcogenides have been explored as promising candidates to be applied in optoelectronics, photovoltaics and energy storage devices. In this work, we present a comprehensive theoretical study of sodium molybdenum selenide (Na2MoSe4). First-principles computations were performed on a set of hypothetical crystal structures to determine the ground state and electronic properties of Na2MoSe4. We find that the equilibrium structure of Na2MoSe4 is a simple orthorhombic (oP) lattice, with space group Pnma, as evidenced by thermodynamics. Electronic structure computations reveal that three phases are semiconducting, while one (cF) is metallic. Relativistic effects and Coulomb interaction of localized electrons were assessed for the oP phase, and found to have a negligible influence on the band strucutre. Finally, meta-GGA computations were performed to model the band structure of primitive orthorhombic Na2MoSe4 at a predictive level. We employ the Tran-Blaha modified Becke-Johnson potential to demonstrate that oP Na2MoSe4 is a semiconductor with a direct bandgap of 0.53 eV at the Γ point. Our results provide a foundation for future studies concerned with the modeling of inorganic and hybrid organic-inorganic materials chemically analogous to Na2MoSe4.