四方相BaTiO_3铁电性的第一性原理研究

First-principles study on tetragonal BaTiO_3 ferroelectric

在广义梯度近似下 ,利用超软赝势对立方相和四方相BaTiO3晶胞中Ti原子沿c轴位移时体系的能量、原子间电子云重叠布局数和各原子上的净电荷等进行了自洽计算 .结果显示 ,当Ti原子沿c轴位移 0 0 12nm时 ,四方相BaTiO3体系能量最低 ,其自发极化强度为 0 2 6 1C m2 ,该结果与实验数据相符合 ;同时表明 ,O原子的 2p轨道和Ti原子的 3d轨道的杂化是BaTiO3晶体出现铁电性的重要原因 .

Based on the generalized gradient approximation (GGA), the total-energy, overlap populations and valence charges in the case of Ti atoms moving along c axis in cubic and tetragonal phases were calculated by using ultrasoft pseudopotentials (USP) plane wave method. It was demonstrated that the energy of tetragonal BaTiO3 was the lowest when Ti atoms move along the c axis by up to 0.012nm, and the spontaneous polarization was 0.261C/m(2) , which was consistent with experimental results. Moreover, it was also confirmed that the ferroelectric stability of BaTiO3 could be attributed to the orbital hybridization of 2p orbit of oxygen atom and 3d orbit of Ti atom.