The Electronic Structure and Optical Properties of CdGeAs2 Crystal: A DFT and HSE06 Study

The electronic structural and optical properties of CdGeAs2 crystals are calculated by using the Perdew-Burke-Ernzerhof (PBE) functional within generalized gradient approximation (GGA) and the Heyd-Scuseria-Ernzerhof (HSE06) functional. The results show that CdGeAs2 is an optical crystal with a direct bandgap of 0.71 eV by using the HSE06 functional method, which is closer to the experimental value. The Mulliken population and differential charge density analysis indicate that the Ge-As and Cd-As bonds have covalent properties, and that the covalent bond of Cd-As is visibly stronger than that of the Ge-As bond. The optical properties show that the CdGeAs2 crystal has strong absorption and reflection in the ultraviolet region and strong transmittance in the infrared region. The average static refractive index of CdGeAs2 is 2.96, and the static birefractive index is 0.08. The results show that CdGeAs2 is an excellent optical material of potential applications in the middle and far infrared.