First-principles calculation of rhombohedral perovskite MgAgF3: a DFT study of optical, electronic, elastic, thermodynamic and mechanical properties

Abstract

This research utilizes density functional theory (DFT) to comprehensively explore the structural, elastic, electronic, optical, thermodynamic and mechanical characteristics of the halide perovskite MgAgF₃, which crystallizes in a rhombohedral lattice that belongs to the trigonal crystal system. Elastic constant evaluations confirm mechanical stability and ductility (Pugh's ratio = 2.14, Poisson's ratio = 0.28), alongside slight elastic anisotropy (A^U = 0.07369). Band structure calculations reveal an indirect bandgap of 2.16 eV using GGA-PBE, with electronic states near the Fermi level dominated by hybridized Ag-4d and F-2p orbitals, indicating mixed ionic-covalent bonding. Optical analysis reveals pronounced anisotropy, a refractive index between 1.5 and 1.7, and significant ultraviolet absorption in the 8–12 eV range, with a marked energy-loss peak at 63 eV signifying strong plasmon resonance. Phonon dispersion affirms dynamic stability and thermodynamic predictions, and the consistency with Debye theory shows regular heat capacity behavior. The machinability index (2.093) and ductile behavior suggest suitability for practical processing. Despite being computational, the study lays foundational insights into MgAgF₃'s potential in flexible optical and electronic applications, such as polarized light detectors and UV photonic systems, emphasizing the need for future experimental validation.