Ab initio study of electronic, elastic, thermodynamic, photocatalytic properties of double antiperovskite, Cs6AgBiX2 (X = Cl, Br, I)

Abstract

In this paper, we use density functional theory (DFT) using full-potential linearized augmented plan wave plus local orbital method (FP-LAPW + lo). The structural, electronic, optical, photocatalytic, mechanical, vibrational, and thermodynamical behaviors of new double antiperovskite (DAP) Cs₆AgBiX₂ (X = Cl, Br, I) were studied. The band structure was calculated with and without spin orbit coupling (SOC). Using the TB-mBJ approach (Hybrid) revealed bandgap values of 1.504 eV, 1.491 eV, and 1.392 eV for Cs₆AgBiCl₂, Cs₆AgBiBr₂, and Cs₆AgBiI₂, respectively. Optical characteristics were studied to ascertain the light absorbing ability of Cs₆AgBiX₂. The elastic and vibrational (phonon) properties demonstrate that Cs₆AgBiCl₂ and Cs₆AgBiBr₂ are stable but Cs₆AgBiI₂ is not. The calculated optimal bandgap and high absorption coefficient of Cs₆AgBiCl₂ and Cs₆AgBiBr₂, suggest their potential for solar cell applications. Moreover, our photocatalytic results suggest that these materials have high oxidizing capacity that can be used to efficiently produce oxygen cheaply using solar water splitting.