中文摘要：

采用基于第一性原理的赝势平面波方法计算了M’型和M型YTaO4的电子结构、介电函数、折射率、吸收光谱。计算结果表明：二者价带的贡献都主要来源于O2p态，导带主要由Ta5d态和Y4d态组成；M’型和M型YTaO4的静态介电常数相差较大，介电函数虚部特征峰分别对应于不同的带间跃迁；两种结构的YTaO4在紫外区的吸收带宽而强，此吸收带归属于从氧到d^0电子的电荷转移跃迁。最后从带隙的角度对X射线激发下M’和M型YTaO4：RE^3＋的辐射效率进行了分析，得出M’型YTaO4：RE^3＋辐射效率比M型更为优越的原因之一在于其相对较窄的带隙宽度，所以在X射线CCD的应用上，M’型更为优越。

英文摘要：

Electronic structures, dielectric functions, refraction indices, absorption spectra of M＇ type and M type YTaO4 crystals are calculated using pseudo-potentials and plane waves based on first-principles method. The results show that valence band both originates from O2p states. Conduction band is mainly composed of Ta5d states and Y4d states. The difference of static dielectric constant between M＇ type and M type is large. The peaks of their imaginary parts originate from different interbands transition. Last but not the least, the ultraviolet absorption bands of M＇ type and M type YTaO4 are broad and strong. They correspond to the charge transfer transition from oxygen to do ions of tantalum. At last, radiant efficiency of M＇ type and M type YTaO4 ：RE^3＋ under X-ray excitation are analyzed based on the band gap. One of the reasons for the radiant efficiency superiority of M＇ type YTaO4 ：RE^3＋ to that of M type is that the band gap of the former is narrower. Therefore, M＇ type is better on the application of X-ray CCD.