Computational Study of Elastic, Structural, Electronic, and Optical Properties of GaMF (M = Be and Ge) Fluoroperovskites, Based on Density Functional Theory.

This paper explains our first-principle computational investigation regarding the structural, optical, elastic, and electrical characteristics of gallium-based GaMF (M = Be and Ge) perovskite-type (halide-perovskite) compounds. Our current computation is based on density functional theory (DFT) and is achieved with the help of the WIEN2k code. We used the Birch-Murnaghan equation for optimization; in both compounds, we found that both GaBeF and GaGeF compounds are structurally stable. For the computation of elastic characteristics, the IRelast package for calculating elastic constants (ECs) is utilized. These compounds are mechanically ductile, scratch-resistant, anisotropic, and mechanically stable, showing huge opposition to plastic strain. The modified Becke-Johnson (TB-mBJ) potential approximation method is used to calculate different physical characteristics and shows that GaGeF behaves as a metal, whereas the GaBeF compound is insulating in nature. The involvement of various electronic states in band structures is calculated using the theory of the density of states. The different optical properties of these compounds can be studied easily using their band gap energy. At high energy ranges, these substances demonstrate strong absorption. At low energies, the GaGeF compound is transparent, while the GaBeF compound is opaque to incoming photons. Investigation of the optical characteristics has led us to the conclusion that both GaGeF and GaBeF compounds can be used for high-frequency ultraviolet device applications. This computational work is considered to be the first time that we can study these compounds, which to our knowledge have not previously been experimentally validated.