The relationship between covalent bonds and the optical response in a nonpolar family ATeMoO₆ (A=Mg, Zn, Cd): A Berry-phase investigation

Highlights: • Chemical bonds are analyzed by DOS, atomic charges and Mulliken bond populations. • Refractive indices and SHG output is investigated by variation of atomic charge and chemical bonds. • Birefringence is investigated by Born effective charges. • Robust covalent bonds play an important role in determining the refractive indices and SHG response. • Anisotropic electron distributions on covalent Te-O and Mo-O bond give main contribution to birefringence. - Abstract: The macroscopic polarization, the refractive indices, birefringence, and the second-order nonlinear optical susceptibilities in a family of nonpolar materials ATeMoO₆ (A = Mg, Zn, and Cd) have been investigated using the Berry-phase calculation. The microscopic origin of the optical response is further investigated by the variation of atomic charge, the Born effective charges, and the chemical bond analyses based on the Bader charge analysis and the Mulliken bond population analysis. The results show that the robust covalent bonds play an important role in determining the refractive indices and SHG response, and the anisotropic electron distributions on covalent Te‒O and Mo‒O bond give main contribution to the optical anisotropic birefringence.