BaTiO_3的电子结构和光学性质(英文)

Electronic Structures and Optical Properties of BaTiO_3

采用第一性原理赝势平面波方法,在局域密度近似(LDA)和广义梯度近似(GGA)下分别计算了BaTiO3立方相和四方相的电子结构,并在局域密度近似下计算了BaTiO3立方相的光学性质.结果表明,BaTiO3立方相和四方相都为间接带隙,方向分别为Γ-M和Γ-X,大小分别为2.02和2.20eV.对BaTiO3和PbTiO3铁电相短键上电子布居数的对比分析,给出了它们铁电性大小的差别.且在30eV的能量范围内研究了BaTiO3的介电函数、吸收系数、折射系数、湮灭系数、反射系数和能量损失系数等光学性质,并基于电子能带结构对光学性质进行了解释.计算结果与实验数据相符合.

The pseudo-potential plane wave （PP-PW） method, the local density approximation （LDA） and generalized gradient approximation （GGA） were used to calculate the electronic structures of cubic and tetragonal BaTiOa, respectively. The local density approximation was used to calculate optical properties of cubic BaTiO3. Results show an indirect bandgap of 2.02 eV in the Г-M direction for the cubic phase and an indirect bandgap of 2.20 eV in the Г-X direction for the tetragonal phase. For ferroelectric phases, a comparison of shorter bond populations for BaTiO3 and PbTiO3 revealed differences in ferroelectric behavior between BaTiOa and PbTiO3. Furthermore, the dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity, and energy loss coefficient were obtained and analyzed on the basis of electronic band structures for radiation of up to 30 eV. These results are in good agreement with experimental data.