Electronic and optical properties of lithium niobate under high pressure: A first-principles study  

作　　者：桑丹丹 王庆林 韩崇 陈凯 潘跃武 

机构地区：[1]Mathematics and Physical Sciences Technology,Xuzhou Institute of Technology [2]Center for High Pressure Science and Technology Advanced Research

出　　处：《Chinese Physics B》2015年第7期420-425,共6页中国物理B（英文版）

基　　金：Projects supported by the National Natural Science Foundation of China(Grant Nos.11347154 and 51172194);the Foundation of Xuzhou Institute of Technology,China(Grant No.XKY2013203)

摘　　要：We theoretically study the structural, electronic, and optical properties of lithium niobate under pressure using the plane-wave pseudopotential density functional theory by CASTEP code. It was found that there is a phase transition from the R3 c structure to the Pnma structure at a pressure of 18.7 GPa. The Pnma structure was dynamically stable according to the calculation of phonon dispersion. From the charge density distributions, there exist covalent interactions along the Nb–O bond. The hybridization between O 2p and Nb 4d orbital in the Pnma phase increases with increasing pressure, while it is not changed in the R3c phase. With increasing pressure, the average Nb–O bond length decreases and the Nb–O bond population increases, indicating the increased covalent character between Nb and O atoms under high pressure at Pnma phase, which leads to the increased hybridization between O 2p and Nb 4d orbitals. Furthermore, the optical dielectric function, refractive index, extinction coefficient, electron energy, loss and reflectivity are calculated.We theoretically study the structural, electronic, and optical properties of lithium niobate under pressure using the plane-wave pseudopotential density functional theory by CASTEP code. It was found that there is a phase transition from the R3 c structure to the Pnma structure at a pressure of 18.7 GPa. The Pnma structure was dynamically stable according to the calculation of phonon dispersion. From the charge density distributions, there exist covalent interactions along the Nb–O bond. The hybridization between O 2p and Nb 4d orbital in the Pnma phase increases with increasing pressure, while it is not changed in the R3c phase. With increasing pressure, the average Nb–O bond length decreases and the Nb–O bond population increases, indicating the increased covalent character between Nb and O atoms under high pressure at Pnma phase, which leads to the increased hybridization between O 2p and Nb 4d orbitals. Furthermore, the optical dielectric function, refractive index, extinction coefficient, electron energy, loss and reflectivity are calculated.

关 键 词：PRESSURE electronic structure optical properties HYBRIDIZATION 

分 类 号：O521[理学—高压高温物理]