First-Principles insights to probe structural and opto-electronic properties of AgYF3 (Y=Mg, Sr) halide perovskites with variety of DFT methods

This study reports the structural, electronic, optical, phonon, thermodynamic and thermoelectric properties of ${\mathrm{AgYF}}_3$ (X=Mg, Sr) for photovoltaic and energy applications. We performed first principles calculations using full potential linearized augmented plane wave, FP-LAPW method implemented in Wien2k. The generalized gradient approximations of Perdew–Burke–Ernzerhof PBE-GGA, and PBE revised for solids, PBEsol, is employed for structural optimization of these lead free halide perovskites. The Birch–Murnaghan energy volume curve fitting comprehend the structural stability. The optimized lattice constant of ${\mathrm{AgMgF}}_3$ and ${\mathrm{AgSrF}}_3$ obtained with PBE-GGA(PBEsol) is 3.99(3.92) Å and 4.42(4.65) Å. The stability is further tested with the help of formation energy and positive phonon dispersion curves calculations. For the calculations of explicit electronic and optical properties, we also employed Tran–Blaha modified Beck–Johnson (TB-mBJ) and Strongly Constrained but Appropriately Normed, SCAN, exchange and correlations functionals. The electronic band gap of ${\mathrm{AgMgF}}_3$ computed with PBEsol, TB-mBJ and SCAN is 1.96 eV, 5.25 eV and 2.59 eV exhibiting M-$\Gamma$ indirect band gap. The band gap energy of ${\mathrm{AgSrF}}_3$ is 2.06 eV, 6.42 eV and 2.70 eV with PBEsol, TB-mBJ and SCAN. The indirect band gap nature of ${\mathrm{AgSrF}}_3$ is confirmed by PBEsol and TB-mBJ while it anticipated direct band gap behavior with meta-GGA SCAN. The different optical parameters like dielectric constant, optical conductivity, energy loss function, absorption, reflectivity and refractive index are calculated to assess optical activity of both perovskites. Comprehensive electronic and optical analysis advocates the utility of ${\mathrm{AgMgF}}_3$ and ${\mathrm{AgSrF}}_3$ for different applications is solar technology and optoelectronic devices.