Density functional theory analysis of the structural, electronic, elastic, phonon dispersion and AIMD properties of KMgX (X = O, S, Se).

Perovskite chalcogenides have attracted significant interest due to their potential applications in optoelectronics, catalysis, and renewable energy systems. This paper examines the structural, electronic, elastic, and phononic properties of KMgX (X = O, S, Se) using density functional theory (DFT) in the context of the full-potential linearized augmented plane wave plus local orbital (FP-LAPW + lo) approach. Their stability in the cubic phase (3̄ symmetry) is confirmed by the computed lattice parameters for KMgO (4.1325 Å), KMgS (5.0008 Å), and KMgSe (5.2070 Å). KMgO exhibits semiconducting behavior with a direct bandgap of 7.323 eV in the spin-up state, according to electronic band structure studies, whereas KMgS and KMgSe show metallic properties. Elastic constants (C, C, and C) meet the requirements for mechanical stability, which is evaluated using the Born criterion. Upon further examination of mechanical characteristics such as Bulk modulus, Shear modulus, Young's modulus, and Poisson's ratio. Materials such as KMgO and KMgS exhibit ductile behavior, whereas KMgSe exhibits brittleness. Phonon dispersion curves and molecular dynamics simulations confirm the dynamical and thermal stability of these compounds. The results show that KMgX perovskites have potential uses in optoelectronic devices and spintronics.