Influence of alkaline-earth metals (B = Be, Mg, Ca) doping on the structural, electronic, optoelectronic, thermodynamic, and core-level spectroscopic studies of CsBCl3 halide perovskites

In this study, we employed first-principles density functional theory (DFT) to study the physical properties of the cubic alkali halide perovskite ABX3 (where A = Cs, B = Be, Mg, Ca and X = Cl3). These properties were investigated using the density functional theory (DFT) using quantum expresso code and density function perturbation theory (DFPT) based on Cambridge Serial Total Energy Package (CASTEP).The lattice parameter of the cubic perovskite obtained correlated with other experimental and theoretical works. The Goldschmidt tolerance values of the perovskites were recorded at 1.13, 0.96 and 0.90, respectively, within the acceptable range which confirmed the structural stability of the perovskites. The band structure of the compounds were computed using the Perdew–Burke–Ernezerhof (PBE) exchange–correlation function of the generalized gradient approximation (GGA). The electronic properties give insight on the suitability of a material for the fabrication of modern opto-electronic devices. The lower band gap values obtained for the studied perovskites indicated their semi-conducting abilities and their potential application in the fabrication of solar cell devices. The computed partial density of states (PDOS) showed the hybridization of the atomic orbital of the Cs 4d, the Cl s and p orbitals with marginal contributions from Be, Mg and Ca. The dielectric nature of the perovskites can be deduced from the values of the real dielectric function derived at zero energy which indicates their possible application as optoelectronic materials. The phonon dispersion determines the dynamic stability or instability of the perovskite. The phonon dispersion plot of CsMgCl3 showed complete absence of imaginary phonon states at zero frequency indicating its stability. Detailed investigation of the elastic behaviour of the cubic perovskites revealed that their elastic properties satisfied the Bohn stability criteria, the three cubic perovskites were ductile as their values exceeded the Poisson’s (υ) and the Pugh’s ratio (Bo/G) critical limit of 0.26 and 1.75, respectively, indicating the perovskites are promising candidates for the fabrication of novel solar devices. Molecular dynamics (MD) simulation plots at a constant temperature of 500 K established a stability trend for all the cubic perovskites indicating the thermal stability of the three cubic perovskites. The specific heat, Grüneisen parameter, bulk modulus and the Debye temperature were computed as a function of temperature set at 0–1000 K by employing the Quasi Debye model. X-ray analysis reflected the metallic character of the perovskites.