›› 2014, Vol. 23 ›› Issue (12): 127102-127102.doi: 10.1088/1674-1056/23/12/127102

• CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES • 上一篇    下一篇

The electronic structures, Born effective charge tensors, and phonon properties of cubic, tetragonal, orthorhombic, and rhombohedral K0.5Na0.5NbO3: A first-principles comparative study

周树兰a, 赵显b, 江向平a, 韩晓东a   

  1. a Department of Material Science and Engineering, Jingdezhen Ceramics Institute, Jingdezhen 333403, China;
    b State Key Laboratory of Crystal Material, Institute of Crystal Material, Shandong University, Jinan 250100, China
  • 收稿日期:2014-03-13 修回日期:2014-08-01 出版日期:2014-12-15 发布日期:2014-12-15
  • 基金资助:
    Project supported by the Jiangxi Provincial Natural Science Foundation, China (Grant No. 20122BAB216007) and the Foundation of Jiangxi Provincial Educational Committee, China (Grant No. GJJ14648).

The electronic structures, Born effective charge tensors, and phonon properties of cubic, tetragonal, orthorhombic, and rhombohedral K0.5Na0.5NbO3: A first-principles comparative study

Zhou Shu-Lan (周树兰)a, Zhao Xian (赵显)b, Jiang Xiang-Ping (江向平)a, Han Xiao-Dong (韩晓东)a   

  1. a Department of Material Science and Engineering, Jingdezhen Ceramics Institute, Jingdezhen 333403, China;
    b State Key Laboratory of Crystal Material, Institute of Crystal Material, Shandong University, Jinan 250100, China
  • Received:2014-03-13 Revised:2014-08-01 Online:2014-12-15 Published:2014-12-15
  • Contact: Zhou Shu-Lan E-mail:zhoushulan2009@126.com
  • Supported by:
    Project supported by the Jiangxi Provincial Natural Science Foundation, China (Grant No. 20122BAB216007) and the Foundation of Jiangxi Provincial Educational Committee, China (Grant No. GJJ14648).

摘要: The electronic structures, Born effective charges (BECs), and full phonon dispersions of cubic, tetragonal, orthorhombic, and rhombohedral K0.5Na0.5NbO3 are investigated by the first principles method based on density functional theory. The hybridized states of Nb 4d and O 2p states are observed in the valence band, showing the formation of a strong Nb–O covalent bond which should be responsible for the displacement of Nb and O atoms. The abnormally large BECs of Nb and O indicate the possibility of phase instability induced by the off-center displacement of Nb and O atoms. The phonon dispersions reveal that the ferroelectric instability of K0.5Na0.5NbO3 is dominated by Nb and O displacements with significant Na characteristics. In addition to the ferroelectric instability, there is also rotational instability coming from the oxygen octahedra rotation around one axis. Moreover, the Γ phonon properties of orthorhombic KNbO3, NaNbO3, and K0.5Na0.5NbO3 are also studied in detail.

关键词: Born effective charge, phonon dispersion, density functional theory (DFT), phase instability of K0.5Na0.5NbO3

Abstract: The electronic structures, Born effective charges (BECs), and full phonon dispersions of cubic, tetragonal, orthorhombic, and rhombohedral K0.5Na0.5NbO3 are investigated by the first principles method based on density functional theory. The hybridized states of Nb 4d and O 2p states are observed in the valence band, showing the formation of a strong Nb–O covalent bond which should be responsible for the displacement of Nb and O atoms. The abnormally large BECs of Nb and O indicate the possibility of phase instability induced by the off-center displacement of Nb and O atoms. The phonon dispersions reveal that the ferroelectric instability of K0.5Na0.5NbO3 is dominated by Nb and O displacements with significant Na characteristics. In addition to the ferroelectric instability, there is also rotational instability coming from the oxygen octahedra rotation around one axis. Moreover, the Γ phonon properties of orthorhombic KNbO3, NaNbO3, and K0.5Na0.5NbO3 are also studied in detail.

Key words: Born effective charge, phonon dispersion, density functional theory (DFT), phase instability of K0.5Na0.5NbO3

中图分类号:  (Electron density of states and band structure of crystalline solids)

  • 71.20.-b
77.84.-s (Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials) 62.60.+v (Acoustical properties of liquids)