The electronic structure and optical properties of BaBiBO4, a promising compound with high birefringence

Birefringence is a crucial parameter for various advanced optical devices like birefringent crystals, and nonlinear optical materials. In this paper, the electronic structures and optical properties of centrosymmetric BaBiBO₄ are investigated using the first-principles method. The results show that BaBiBO₄ could be a good birefringent compound whose birefringence is 0.195 @ 1064 nm and 0.266 @ 532 nm. The spin–orbit-coupling effect plays an important role in electronic structures, leading to downshift and band splitting of the conduction band, resulting in a reduced bandgap of 3.32 eV and enhanced birefringence. The projected density of states and real-space atom-cutting results reveal that BiO₅ groups with asymmetric distribution of stereochemical active lone pairs and the staggered parallel arrangement of the BO₃ groups give the main contribution to birefringence.