插层化合物Ag1/4TiSe2电子结构的第一性原理研究

First-principle study on the electronic structures of intercalation compound Ag_(1/4)TiSe_2

采用基于密度泛函理论的平面波赝势方法,选用局域密度近似对Ag1/4TiSe2及TiSe2的几何结构进行了优化和总能量计算.计算得到的晶格常量与实验结果符合较好,负的形成能表明有序Ag1/4TiSe2系统的稳定性.布居数、键长、能带结构和态密度的计算结果显示:Ag以较强的离子性结合于Ag1/4TiSe2中.Ag的插入使得半金属性的TiSe2变为金属性的Ag1/4TiSe2,导电性质得到明显改善.

Geometry optimization and total energy computation of Ag1/4 TiSe2 and TiSe2 have been completed by means of plane wave pseudopotential method based on the local density approximation to density functional theory. The calculated lattice parameters accords with the experimental results reported and the negative formation energy shows the stability of ordered Agl/4 TiSe2 system. The atomic populations, bond lengths, band structure and density of states indicate that： Ag atoms are bonded with stronger ionicity in Ag1/4TiSe2 than in TiSe2. The intercalation of Ag makes TiSe2 with semimetal property change into Ag1/4 TiSe2 with metal property and the conductivity is remarkably improved.