Density functional theory study on the structural, electronic, optical and photocatalytic properties of BaTa₂O₆, Ba₂Ta₁₅O₃₂, Ba₃Ta₅O₁₅ and Ba₅Ta₄O₁₅

By means of density functional theory calculations, we investigated the structural, electronic, optical properties and photocatalytic activity of BaTa₂O₆, Ba₂Ta₁₅O₃₂, Ba₃Ta₅O₁₅ and Ba₅Ta₄O₁₅ four barium tantalum oxides and made a comparative study of them. The results show that these four compounds are indirect band gap semiconductors and the interactions between atoms are weak. They show the superior absorption performance in the ultraviolet region, especially Ba₂Ta₁₅O₃₂ and Ba₃Ta₅O₁₅. Among the four compounds, BaTa₂O₆ and Ba₃Ta₅O₁₅ have the electrons mobility and the recombination rate of the electron-hole pairs in the G→K and G→X directions, respectively. They have the superiority in degrading organic pollutants, especially BaTa₂O₆ on account of its highest valence band potential. Because of the excellent absorption performance and suitable band edge position, it is predicted that BaTa₂O_6, Ba₃Ta₅O₁₅ and Ba₅Ta₄O₁₅ should have the better photocatalytic activity compared with Ba₂Ta₁₅O_32.