中文摘要：

采用基于密度泛函理论（DFT）的第一性原理计算研究了（Ba0.5Sr0.5）TiO3（BST）晶体在高压下的电子结构及能带变化行为.研究结果发现,随着压强的增加,BST能带间隙先增加,在压强为55GPa时达到最大值,然后减小,这些有趣的结果将有助于开发与设计新的BST铁电器件.进一步地,通过电子态密度和密度分布图的研究分析可知：在低压区域（0〈P〈55GPa）,带隙的增加是由于费米能级附近导带反键态的形成和价带成键态的形成共同作用的结果.在高压区域（P〉55GPa）,则是出现的离域现象占主导（电子的离域作用超过键态的作用）,从而使带隙减小.

英文摘要：

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 （0P55 GPa）,the increase in band gap is due to the formation of anti-bonding states and bonding states in the conduction band and valence band,respectively.In the high-pressure region （P55 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.