第一性原理对CaTiO3和CaCu3Ti4O12的对比研究

通过Ca替换CaCu_3Ti_4O_(12)晶胞中的所有Cu,建立了包含TiO6八面体扭转的CaTiO3;通过Cu替换CaTiO32×2×2超胞中3/4的Ca,建立了不包含CuO_4正方形的CaCu_3Ti_4O_(12)。采用Materials Studio软件的CASTEP模块,对比了上述晶体和标准晶体成键状况、能带结构、态密度及介电函数,分析了TiO6八面体扭转和CuO_4正方形的影响,发现了Cu-O键或CuO_4正方形对CaCu_3Ti_4O_(12)光频介电常数的关键性作用。研究结果提供了通过内禀机制优化CaCu_3Ti_4O_(12)材料介电性能的新途径。

Comparative Study of CaTiO3 and CaCu3Ti4O12 by First Principles

In order to reveal the influence of twisted TiO₆ octahedrons and CuO₄ squares on dielectric properties of CaCu₃Ti₄O₁₂, CaTiO₃ and CaCu₃Ti₄O₁₂ were investigated comparatively by First principles. Based on the crystal cell of CaCu₃Ti₄O₁₂, CaTiO₃ crystal cell with twisted TiO₆ octahedrons was built by substituting Ca for all the Cu atoms. Based on 2×2×2 supercell of CaTiO₃, CaCu₃Ti₄O₁₂ crystal cell without CuO₄ squares was built by substituting Cu for 3/4 of the Ca atoms. CASTEP module in First principle calculation software of Materials Studio was used to investigate the difference in bonding, energy band structure, state density and dielectric function for the crystals mentioned above and normal CaTiO₃ and CaCu₃Ti₄O₁₂ crystals. The influence of twisted TiO₆ octahedrons and CuO₄ squares for perovskite was analyzed. It was found that Cu-O bonds or CuO₄ squares play a key role in optical frequency dielectric permittivity of CaCu₃Ti₄O₁₂. The research of this paper offers a new route to optimize dielectric properties of CaCu₃Ti₄O₁₂ by intrinsic mechanism.