Structural stability, band structure and optical properties of different BiVO₄ phases under pressure

Bismuth vanadate (BiVO₄) is a promising candidate material for photocatalytic hydrogen generation and photocatalytic degradation of organics. BiVO₄ has four phases in nature: tetragonal-1, tetragonal-2, orthogonal and monoclinic. In this paper, first-principle calculations were performed to investigate their structural stability, band structures and optical properties. It is illustrated that the stable phase is pressure-dependent and the most stable ones are T-1 (under 0 GPa), T-2 (under 2 GPa) and M phase (under 4, 6 and 8 GPa). BiVO₄ in all cases are indirect band-gap semiconductors and the band gaps decrease with increasing pressure. Moreover, the external pressure might enhance hybridization of O 2p, V 3d and Bi 6s orbitals, and shift the band edges to lower energies. As a result, the optical curves, such as, dielectric function, optical reflectivity, absorption coefficient and refractive index, red shift with pressure in the low energy region, and BiVO₄ in T-2 and M phases has almost the same optical properties in spite of different lattice structures. So the optical properties of BiVO₄ could be tuned by changing pressure to some degree, which is beneficial to the optical applications.