BaVS3晶格动力学研究  

The lattice dynamics of BaVS_3 compound

作　　者：苗仁德[1] 田苗[1] 黄桂芹[1] 

机构地区：[1]南京师范大学物理科学与技术学院

出　　处：《物理学报》2008年第6期3709-3713,共5页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:10447115)资助的课题~~

摘　　要：采用基于密度泛函理论的平面波赝势方法,在局域密度近似下采用线性响应的密度泛函微扰理论研究了具有六角结构的BaVS3化合物的晶格动力学性质,得到了整个声子谱.计算得到的Γ点拉曼频率和实验数据进行了比较,其中E22g模、A1g模和实验测量值符合得比较好.对于E23g模,采用线性响应计算的结果与实验值差别较大.对该模应用冻结声子方法研究后认为差异主要是由于E23g模的较强的非谐性引起的.此外V原子在平面内的振动模E21u出现了虚频.虚频的出现预示着六角相的BaVS3结构的不稳定性,从而很好地解释了该材料由六角相到正交相的结构相变.The lattice dynamics of hexagonal perovskite BaVS3 compound is studied by first-principles calculations based on the ab initio pseudopotential and plane wave basis. Phonon spectra throughout the Brillouin zone are obtained using the density-functional perturbation method within the framework of linear response theory. The calculated frequencies of the Raman active modes are compared with the experimental measurements. For E22g and A1g modes, our calculated values are in good agreement with the experiment. But for E32g mode, the value of the calculated frequency differs significantly from the experiment. After further calculation using the frozen-in phonon method, we suggest that this difference is caused by the large anharmonicity of E32g mode. The most prominent feature of the phonon spectrum is that there appears the imaginary frequency for E12u mode, which involves the planar vibration of the vanadium atoms. The appearance of imaginary frequency for E12u mode indicates the planar instability of hexagonal BaVS3 crystal structure. We believe that this soft mode is responsible for the observed hexagonal-orthorhombic phase transition.

关 键 词：晶格动力学 密度泛函 赝势方法 BaVS 

分 类 号：O481[理学—固体物理]