First-Principles Study On The Stability Of Ordered Structures Of Intercalation Compound Li_xTiS₂

In this thesis the study is aimed at the research on the structural stability and other problems of intercalation compound caused by the fact of the order-disorder phase transition of intercalation compounds and decisive effect on material property by the ordered structures of intercalated ions.Materials Studio using which this article studies ordered structure models that were determinate by the probability wave theory is an advanced stimulation and calculation software which is based on density functional theory that is one of first-principles. Firstly that the ordered structures are constructed by Visualizer according to the parameters of crystal structures in experiment. Secondly appropriate parameters are set and then the structures are calculated in geometry optimization by CATEP. The parameters and energy of lattices are gained, then the band structures and the density of state are analysed, at last the conclusions are gained.In the result something important is founded: in triangular lattices, the 3^1/2a₀×3^1/2a₀ ordered structure is the stablest structure. As the Li ions concentration increase the value of c₀ increases monotonously. The theoretical results are consistent with the experimental results. There is something sufficiently illustrated that the intercalation of Li ion have an important influence on the lattice parameter. This influence is attributed to the strong interaction between Li and TiS₂.In hexangular honeycomb lattices as the Li ions concentration increase the value of the c₀ firstly increase then decrease. This cause by the screen of the S atoms.The tables of DOS of 3D structure are similar as which of 2D structure in shape but the values are very different. The value of the conduction band widths of 3D are smaller than that of the corresponding 2D structures, that indicate the conductive property of 2D structure is great than that of 3D structure. Analysis is that the DOS of 3D structures are the perturbation on the DOS of 2D structures. So two structure tables of DOS are similar. Because the Li ions of very other layer are removed that cause conductive electrons decrease largely, so the conduction property of 3D structure decrease obviously.