中文摘要：

利用第一性原理计算了立方相萤石TiO2的晶胞参数，能带结构和电子态密度。结果显示萤石TiO2属于间接带隙半导体材料，其间接禁带宽度（Г→χ）ER为2．07eV，比常见的金红石和锐钛矿TiO2的禁带宽度窄．为了更清楚地了解萤石的光学性质，利用Kramers-Kmnig色散关系，分别对萤石和金红石TiO2的复介电常数、吸收率等参数进行了计算，并将二者结果做了比较，其中萤石TiO2的静介电常数为8．31．金红石TiO2的静介电常数表现为各向异性ε1xy（0）=6．01和ε1z（0）=7．07，该计算结果与实验值一致。吸收光谱的对比结果显示萤石结构在51nm和153nm处增加了新的吸收峰，并且吸收光谱范围已扩大到了可见光区。

英文摘要：

We calculated the band structure and density of states of fluorite type TiO2 using density functional theory. The results show that fluorite type TiO2 is an indirect-band-gap semiconductor, and its indirect band gap Eg=2.07 eV is smaller than that of rutile or anatase TiO2 . To make optical properties clear, we calculated the complex dielectric constant of fluorite-structured TiO2 and compared it with the rutile TiO2 . The results illustrate that the fluorite TiO2 has a large static dielectric constant of 8.31, and ε1xy （0） = 6.01 and ε 1z（0） = 7.07 for futile TiO2 show excellent agreement with experimental data. Also, two new absorption peaks located at 51nm and 153nm respectively were observed and the absorption range of fluorite TiO2 extends to the visible region.