First-principles Calculation of Electronic Structure, Chemical Bonding and Optical Properties of -Agbis2

We investigated the structural, electronic, chemical bonding, and optical properties of beta-AgBiS2 crystal by using the Perdew-Burke-Ernzerhof (PBE) functional and the hybrid functional Heyd Scuseria Ernzerhof (HSE) within the DFT formalism. The electronic band structures obtained by both methods indicate that beta-AgBiS2 is an indirect band gap semiconductor with band gap of 0.571 and 1.025 eV, respectively. The electron density difference and Mulliken overlap population show that the Ag-S bonds and Bi-S bonds are both ionic bonds. The calculated optical absorption spectrum prove that beta-AgBiS2 is a promising material for solar photovoltaic conversion.