VO_2金属-绝缘结构相变第一性原理研究

First Principles Investigation of the Metal-Insulator Structural Phase Transition of VO_2

基于密度泛函理论和密度泛函微扰理论的第一性原理计算了R相和M1相VO2的电子能带结构和声子色散关系.计算发现:R相VO2的金属性主要来自于未满的t2g轨道中能量最低的3条轨道,当温度低于340 K时,由于V原子链的二聚化和扭曲作用使M1相中的2条t2g轨道降至费米能级以下,从而使M1相表现出半导体特性;在VO2的声子色散谱中沿ΓM和ΓZ方向出现了明显的声子软模,导致这一软模出现的原因是晶体中的电-声相互作用;因此,电-声相互作用是导致VO2金属-绝缘结构相变的直接原因.

This paper presents a first principle investigation of the electronic structures and the phonon dispersion relationships of VO2 within the framework of density functional theory and density functional perturbation theory.The energy band structures showing that the metallic property of rutile VO2 is mainly due to the three lowest t2g bands in the V 3 d states.While,because of the dimerization and the twisting of the V atomic chain,at T = 340K,the VO2 transformed from metal to insulator.In the phonon dispersion spectrums of the rutile VO2,it is found that significant soft modes both in the ΓM and ΓZ directions which strongly indicate that the electron-phonon coupling triggers the metal-insulator structural phase transition.