Density functional theory (DFT) based on the pseudo-potential plane wave basis set was used to investigate the electronic structures and optical properties of CuAIX2 (X=S, Se, Te) crystals with a chalcopyrite structure. The results indicate that these compounds have a similar band structure and the bandgap decreases from S to Te. Except for the static birefringence, which is just opposite to a change in the bandgap, the static dielectric constant, refractive index and second harmonic generation (SHG) coefficient d36 of this series of compounds increased from S to Te. The SHG response of the three semiconductors can be attributed to transitions from the occupied bands near the top of the valence band to the unoccupied bands that are contributed to by the p states of the Al and X atoms. Among the three crystals, the optical properties of the CuAITe2 crystal are better than those of CuAIS2 and CuAISe2 crystals except that the corresponding static birefringence is too small.%采用基于赝势平面波基组的密度泛函理论方法,研究具有黄铜矿结构的CuAlX2 (X=S,Se,Te)晶体的电子结构,并预测了它们的线性和非线性光学性质.结果表明:这些化合物具有相似的能带结构,带隙随X原子从S→Se→Te 依次减小.三种晶体的静态介电常数、静态折射率和静态倍频系数d36的变化情况与带隙的变化相反,随着X原子自S→Se→Te改变依次递增,但静态双折射率依次递减.该系列化合物的倍频效应主要来源于价带顶附近的占据能带向以Al 和X原子的p 电子态为主要成分的空带之间的跃迁.在三种晶体中,CuAlTe2除静态双折射率偏小外,其它光学性能要优于CuAlS2和CuAlSe2.
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