Specific features of band structure and optical anisotropy of Cu ₂CdGeSe₄ quaternary compounds

Complex theoretical and experimental studies of the band structure and optical functions of a new Cu₂CdGeSe₄ quaternary crystal are reported. The benchmark band structure calculations were performed using the first-principles methods. As a result, the structural, electronic, optical and elastic properties of Cu₂CdGeSe₄ were calculated in the general gradient approximation (GGA) and local density approximation (LDA). The calculated dielectric function and optical absorption spectra exhibit some anisotropic behavior. Detailed analysis of the band energy dispersion and effective space charge density helped in establishing the origin of the band structure anisotropy. All calculated properties are compared with the experimental data. An additional comparison with a similar crystal of Cu ₂CdGeSe₄ allowed to reveal the role played by the anions (S or Se) in formation of the optical properties of these two materials.