中文摘要：

从头计算了CuInSe2（CIS）体相的性质,参数设定和性质计算都基于密度泛函理论,交换相关能采用GGA,泛函形式为PBE,原子间相互作用的描述采用超软赝势.计算发现CIS中存在共价键,是一种非典型的离子型晶体,在整个晶体内存在共用电子对,Cu原子和Se原子的作用大于Se原子和In原子.CIS是一种典型的直接带隙半导体,计算得到了光学性质的各项参数,包括折射指数和反射率,吸收系数以及介电函数与光子能量的关系,发现CIS的主要光吸收峰有6个,分别为：3.1,7.6,10.0,16.1,19.0,21.0eV,理论上最强吸收峰在紫外光区.

英文摘要：

In this article, optical and electronic properties of CIS are studied from DFT calculations. For the exchange-correction energy,we employ GGA in the form of RPBE. The interactions between valence electrons and ionic core are represented by the ultrasoft pseudo potential. By analyzing the results, a mixed bonding state is found to exist in CIS, which is a strong ionic bond with a much weaker covalent bond. The interactions between Cu and Se are much stronger than that between In and Se. It was clarified that CuInSe2 has a direct band gap. We also calculate various optical properties of this material, such as reflection index, refraction index, adsorption spectrum and dielectric constant. For the adsorption spectrum, there are six peaks ： 3.1,7.6, 10.0,16.1,19.0 eV,21.0 eV and the strongest adsorption peak is located in ultraviolet region.