Density functional theory investigations of bismuth vanadate: Effect of hybrid functionals

Hybrid density functional theory (DFT) calculations were performed on the monoclinic clinobisvanite polymorph of bismuth vanadate (BiVO4), which has piqued experimental and theoretical interest in recent years due to its photo-active nature. In particular, the effect of using PBEsol and HSE06–PBEsol functional, as corrected for the solid state, is gauged upon the predictive performance for electronic structure, band gap and optical properties. It was found that HSEsol-type functionals offer better predictive performance than PBEsol with respect to experimental data, although PBEsol performs comparatively well for this system, despite its general well-known limitations. Nonetheless, appropriately-tuned HSE06–PBEsol hybrid functionals may provide an improved description of solids compared to PBE, PBEsol and HSE06. Although the ‘standard’ proportion of exact exchange for HSEsol (25%) seems to provide a relatively accurate band gap vis-à-vis experiment, a smaller proportion (circa 10%) achieves quantitative agreement in this respect; in addition, the prediction of the lattice constants and band gaps is improved substantially. For HSE06–PBEsol, analysis of the density of states analysis showed that the conduction-band minimum (CBM) and valence-band maximum (VBM) position shift upwards and downwards, respectively, thus widening the band gap, in better agreement with experimental results. It was found that clinobisvanite is an indirect (albeit closer to a direct) band-gap semiconductor, and the optical properties were investigated, including the effect of varying the proportion of exact exchange thereon.