Electronic and optical properties of mercury-containing borate

Abstract Hg4O(BO2)6 crystal with a special sodalite cage is expected to pose novel physical properties. In this work, its crystal structure, electronic structure and optical properties are investigated by the first-principles calculations. Hg4O(BO2)6 crystal has high Young's modulus and very weak elastic anisotropy. It possesses an indirect band gap of 2.96 eV, and the electronic transitions from the top valence bands of O-2p orbit to the bottom conduction bands of Hg-6s orbit play important roles in the optical properties. High absorption coefficient, low reflectivity and low loss function promise Hg4O(BO2)6 crystal to be used as ultraviolet absorber in photovoltaic devices.