Density functional theory analysis of the structural, electronic, elastic, phonon dispersion and AIMD properties of KMgX3 (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 KMgX₃ (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 (Pmm symmetry) is confirmed by the computed lattice parameters for KMgO₃ (4.1325 Å), KMgS₃ (5.0008 Å), and KMgSe₃ (5.2070 Å). KMgO₃ exhibits semiconducting behavior with a direct bandgap of 7.323 eV in the spin-up state, according to electronic band structure studies, whereas KMgS₃ and KMgSe₃ show metallic properties. Elastic constants (C₁₁, C₁₂, and C₄₄) 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 KMgO₃ and KMgS₃ exhibit ductile behavior, whereas KMgSe₃ exhibits brittleness. Phonon dispersion curves and ab initio molecular dynamics simulations confirm the dynamical and thermal stability of these compounds. The results show that KMgX₃ perovskites have potential uses in optoelectronic devices and spintronics.