Investigation of X₂GaAgCl₆ (X = K, Cs) for Optoelectronic Devices: A Density Functional Theory Study

Abstract

The electronic, elastic, structural, and optical properties of X 2 GaAgCl 6 (X = K, Cs) are investigated by using the full potential linearized augmented plane wave (FP‐LAPW) method based on density functional theory (DFT). Generalized‐gradient approximation (GGA) is used along modified Becke–Johnson (mBJ) exchange potential. K 2 GaAgCl 6 and Cs 2 GaAgCl 6 reveal the direct bandgap ( E g ) of 2.57 and 2.63 eV, respectively, at Γ symmetry points. The negative values of formation enthalpy (−1.694 for K 2 GaAgCl 6 and −1.798 for Cs 2 GaAgCl 6 ) and value of tolerance factor ( τ ) close to unity (0.82 for K 2 GaAgCl 6 and 0.89 for Cs 2 GaAgCl 6 ) confirm the stable nature of X 2 GaAgCl 6 (X = Cs, K) compounds in cubic phase. Optical properties such as absorption coefficient α( ω ), optical conductivity σ ( ω ), reflectivity R ( ω ), extinction coefficient k ( ω ), refractive index n ( ω ), and dielectric constants ( ε 1 and ε 2 ) are calculated. The ε 2 ( ω ) spectrum of Cs 2 GaAgCl 6 and K 2 GaAgCl 6 shows highest absorption peaks at 4.8 and 4.9 eV, respectively. The highest absorption is observed from Cs 2 GaAgCl 6 at 7.44 eV and from K 2 GaAgCl 6 at 7.46 eV energies. It is also noted that A 2 GaAgCl 6 (A = K, Cs) compounds are elastically stable, anisotropic, and ductile. Investigation of elastic, structural, and optical properties shows that the compounds M 2 GaAgCl 6 (M = Cs, K) can be potential candidates for optoelectronic applications.