Acta Phys. -Chim. Sin. ›› 2015, Vol. 31 ›› Issue (6): 1059-1068.doi: 10.3866/PKU.WHXB201504144

• THEORETICAL AND COMPUTATIONAL CHEMISTRY • Previous Articles     Next Articles

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).

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