作　　者： ; ;

机构地区： 天津大学理学院现代材料物理研究所

出　　处： 《物理学报》 2008年第3期1823-1828,共6页

摘　　要： 根据Ag+离子-空位的二维有序结构建立了三维晶胞模型.采用局域密度近似下的平面波赝势方法,对有序AgxTiS2(x=0,1/4,1/3,1/2,2/3,3/4,1)系列进行了几何结构优化和总能量计算,并与LixTiS2系列进行了对比研究.有序AgxTiS2系统的晶格参量增量Δa0和Δc0随离子浓度单调增加,与实验结果符合得较好.有序AgxTiS2和LixTiS2系统的总能量均随插层离子浓度增加线性下降,且前者下降较快.有序AgxTiS2(x=0,1/4,1/3,1/2,2/3,3/4,1)系统的形成能均小于零,表明其基态性质.具有3a0×3a0超结构的Ag1/3TiS2系统的形成能最低.能量性质的对比显示,有序AgxTiS2系统的形成能较低,有序-无序相变温度较高,离子扩散活化能较高.根据计算结果对有关实验给出了合理解释. Three-dimensional cell models are constructed for fast ionic conductor Ag^＋ TiS2 according to the two-dimensional ordered structure of Ag^＋ ion-vacancy. Geometry optimization and total energy computation are performed for ordered Ag^＋ TiS2 （x = 0,1/ 4,1/3, 1/2,2/3,3/4, 1 ）series using plane-wave pseudo-potential method based on local density approximation to densityfunctional theory, and the results are compared with the LixTiS2 series. The increments of lattice parameters △a0 and △c0 increase monotonically with increasing ion concentration, which well accords with experimental results. The total energies of Ag^＋ TiS2 and LixTiS2 system decrease linearly with increasing ion concentration, and the former decreases more rapidly. The negative formation energies of Ag^＋TiS2 （x = 1/4, 1/3, 1/2, 2/3, 3/4）system indicate their ground state property, among which the formation energy of Ag1/3 TiS2 system with √3a0×√3a0superstructure is the lowest. The formation energy of ordered Ag, TiS2 （x = 1/4, 1/3, 1/2, 2/3, 3/4）system is lower than that of LixTiS2 system, implying higher temperature of order-disorder transition and higher activation energy of ionic diffusion. Reasonable explanation for related experimental results are presented according to these computational results.

关 键 词： 有序 无序相变 离子扩散 第一性原理计算 二维基态结构 快离子导体

领　　域： [理学]