Pressure induced band-gap changes in (Ba0.5Sr0.5)TiO3 (BST) from first-principles calculations
立方（Ba_（0.5）Sr_（0.5））TiO_3高压诱导带隙变化的第一性原理研究

The high-pressure behaviors of crystalline (Ba0.5Sr0.5)TiO3 (BST) are investigated, using the first-principles calculations based on the density functional theory. The results show that as pressure increases, the band gap of BST first increases and peaks at around 55 GPa, and then gradually decreases. The analysis of density of states shows that in the low-pressure region (055 GPa), the delocalization phenomenon in dominant due to the fact that the delocaligation action exceeds the force of bonding state and anti-bonding state, which results in the decrease of the band gap.