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 (<i>oP</i>) lattice, with space group Pnma, as evidenced by thermodynamics. Electronic structure computations reveal that three phases are semiconducting, while one (<i>cF</i>) is metallic. Relativistic effects and Coulomb interaction of localized electrons were assessed for the <i>oP</i> 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 <i>oP</i> Na2MoSe4 is a semiconductor with a direct bandgap of 0.53 eV at the <b>Γ</b> point. Our results provide a foundation for future studies concerned with the modeling of inorganic and hybrid organic-inorganic materials chemically analogous to Na₂MoSe₄.<br>