Birefringence, linear and nonlinear second-order optical susceptibilities of a noncentrosymmetric chalcopyrite compound HgGa2S4

We present the results of the ab initio theoretical study of the linear and nonlinear optical susceptibilities for the HgGa2S4 single crystals using the all electron full potential-linearized augmented plane wave (FP-LAPW) method as implemented in the WIEN2K code. We employed generalized gradient approximation (GGA), which is based on exchange-correlation energy optimization to calculate the total energy. We have used the Engel–Vosko GGA formalism, which optimizes the corresponding potential for band structure and optical susceptibilities calculations. Our calculations show that the valence band maximum (VBM) and conduction band minimum (CBM) are located at Γ resulting in a direct energy gap. We present calculations of the frequency-dependent complex dielectric function ε(ω) and its zero-frequency limit ε1(0). The optical properties are analyzed, and the origin of some of the spectral peaks is discussed in terms of the calculated electronic band structure. The edge of optical absorption for ε2xx(ω) and ε2zz(ω) is located at 2.8 eV. The linear optical properties shows a large negative uniaxial anisotropy and birefringence which favors large second-order susceptibility χijk(2)(ω). The imaginary and real parts of the second-order SHG susceptibility were evaluated. Our calculation show that χ213(2)(ω) is the dominant component which shows the largest total  Reχijk(2)(0) valve 5.4 pm/V.