Pb0．5Sr0．5TiO3精细结构的第一性原理分析

FIRST-PRINCIPLE ANALYSYS ON FINE STRUCTURE OF Pb_(0.5)Sr_(0.5)TiO_3

在广义梯度近似下,采用基于密度泛函理论框架下的第一性原理和虚拟晶体近似(VCA)方法,计算了Pb_(0.5)Sr_(0.5)TiO_3 (PST)电子结构及其属性.分析了PST固溶体总体能量变化趋势,确定了A位离子在铁电相的平衡构型.计算结果表明:在PST固溶体中,当Ti原子相对于氧八面体沿[001]方向发生约0.012 nm偏心位移,PST出现能量极小值.O 2p和Ti 3d轨道的强杂化以及部分O—Pb和O—Sr轨道杂化间接增强了TiO_6八面体的畸变,体系总能量降低,促进了PST铁电畴变的形成.

The electronic structures and properties of Pb0.5Sr0.5TiO3 （PST） were calculated by the plane wave ultra-soft pseudo-potential and virtual crystal approximate （VCA） technologies based upon the density function theory （DFT） within the general gradient approximation. The changed trend of the total energy of PST solid solution was analyzed, and the equilibrium configuration of A site cations （Pb and Sr） in the ferroelectric phase was determined. The calculated results revealed that the energy of PST appeared minimum when the off-center displacement of Ti atom was up to 0.012 nm along （001） direction. The strong hybridization between O 2p and Ti 3d and part hybridizations between O--Pb and O- Sr showed an increase in the distortion of TiO6 octahedron and a reduce in the system total energy, which led to the formation of ferroelectric domains.