物理化学学报 >> 2015, Vol. 31 >> Issue (6): 1059-1068.doi: 10.3866/PKU.WHXB201504144

理论与计算化学 上一篇    下一篇

基于第一性原理计算的铁电材料BaTiO3相关振动光谱指认

安炜1, 刘天慧2,3, 王春海2, 刁传玲2, 罗能能2, 刘勇2,3, 戚泽明4, 邵涛4, 王玉银4, 焦桓3, 田光善1, 荆西平2   

  1. 1 北京大学物理学院, 北京100871;
    2 北京大学化学与分子工程学院, 稀土材料化学及应用国家重点实验室, 北京100871;
    3 陕西师范大学化学化工学院, 陕西省大分子科学重点实验室, 西安710119;
    4 中国科技大学, 国家同步辐射实验室, 合肥230029
  • 收稿日期:2015-02-14 修回日期:2015-04-12 发布日期:2015-06-05
  • 通讯作者: 田光善, 荆西平 E-mail:tiangs@pku.edu.cn;xpjing@pku.edu.cn
  • 基金资助:

    国家自然科学基金(21071009, 21371015)资助项目

Assignment for Vibrational Spectra of BaTiO3 Ferroelectric Ceramic Based on the First-Principles Calculation

AN Wei1, LIU Tian-Hui2,3, WANG Chun-Hai2, DIAO Chuan-Ling2, LUO Neng-Neng2, LIU Yong2,3, QI Ze-Ming4, SHAO Tao4, WANG Yu-Yin4, JIAO Huan3, TIAN Guang-Shan1, JING Xi-Ping2   

  1. 1 School of Physics, Peking University, Beijing 100871, P. R. China;
    2 State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China;
    3 Key Laboratory of Macromolecular Science of Shaanxi Province, College of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China;
    4 National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, P. R. China
  • Received:2015-02-14 Revised:2015-04-12 Published:2015-06-05
  • Contact: TIAN Guang-Shan, JING Xi-Ping E-mail:tiangs@pku.edu.cn;xpjing@pku.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21071009, 21371015).

摘要:

通过固相反应烧结法在1400 ℃下烧结4 h合成了BaTiO3陶瓷, 并用X衍射确定了其为四方晶系. 进行了拉曼谱和红外谱的测量, 并采用洛仑兹函数以及四参数方法分别对上述光谱进行了拟合. 基于第一性原理的计算, 并考虑了横模纵模劈裂, 对拉曼和红外光谱进行了指认. 为了更好地分析振动模式, 所有振动模用群论的对称坐标进行了分解. 在12个光学模中, 仅具有拉曼活性的B1模式是O4和O5沿着z轴的相对运动. A1模式和E1软模式是从立方BaTiO3相的F1u模式劈裂出来的, 对于四方相BaTiO3的铁电性有着重要作用, 其体现在A1(1)模式造成了铁电z轴的极化, E1模式导致了大介电常数. 这两个模式都可以看成是Ti 原子相对于O6八面体笼子沿着z轴或者是xy平面的振动.

关键词: 第一性原理计算, 拉曼模式, 红外模式, 介电性质

Abstract:

ABaTiO3 ceramic was synthesized using a conventional solid-state reaction, and sintered at 1400 ℃ for 4 h. The pure tetragonal phase was confirmed by Rietveld refinement of the X-ray diffraction data. The Raman spectrum and the far infrared (FIR) reflective spectrum were obtained and analyzed using Lorentz fitting and the four-parameter semi-quantum model fitting, respectively. The Raman and FIR spectra were assigned based on first-principles calculations, and consideration of the splitting of the transverse optical modes and longitudinal optical modes. All the vibrational modes were represented by linear combinations of the symmetry coordinates deduced by group theory analysis. Among the 12 optical modes, the Raman-active-only mode, B1, can be viewed as the wing-flapping vibration of the O4-O5 plane perpendicular to the z-axis in the O6 octahedron. The A1(1) mode and the E(1) soft mode are split by the triply degenerate F1u mode of cubic BaTiO3, resulting in the ferroelectric property of tetragonal BaTiO3. The appearance of the A1(1) mode leads to crystal polarization along the z-axis and the E(1) mode causes the large permittivity. These two modes can be described as vibration of the Ti atom against the O6 octahedral cage along the z-axis [A1(1)] and on the xy-plane [E(1)].

Key words: First-principles calculation, Raman mode, IR mode, Dielectric property

MSC2000: 

  • O649