DFT-based study on the physical and molecular dynamics properties of some E ₃ IO alkaline-metal anti-perovskites for renewable energy applications

In this work, we employ density functional theory (DFT) to systematically investigate the physical, thermodynamic and dynamical properties of E 3 IO (E[Formula: see text] [Formula: see text] [Formula: see text]K, Rb, Cs, Fr) alkali-metal-based anti-perovskites for next-generation renewable-energy and optoelectronic applications. Our results reveal that the E-site cation strongly governs lattice parameters, bandgaps and formation energies, enabling tunable electronic and optical behavior. K 3 IO, with its wider bandgap and high stiffness, shows potential as a stable solar-cell absorber and rigid optoelectronic material, while Rb 3 IO and Cs 3 IO, exhibiting intermediate bandgaps and balanced mechanical properties, are promising for tandem photovoltaics, UV–visible photonic devices and thermal storage. Fr 3 IO, though theoretically informative, highlights the influence of large cations on dielectric and vibrational behavior but is experimentally limited by francium’s radioactivity. Phonon dispersion, molecular dynamics and thermodynamic analyses confirm dynamic and thermal stability across the series, reinforcing their suitability for real-world operating conditions. Collectively, these findings provide a comprehensive framework for designing lead-free anti-perovskites with tailored properties for renewable-energy and optoelectronic devices.