Linear and nonlinear optical susceptibilities in some ferroelectrics: Ab-initio calculation

We present a first principles calculations of the second-order optical response functions as well as the dielectric function for ABO3 (A=K, Li, Ba; B=Ti, Ta, Nb) and A5B6C7 ( A=Sb; B=S, Se; C=I, Br ) ferroelectrics. Specially, we evaluate the dielectric function ε(ω) =ε1(ω)-iε2(ω)and the second harmonic generation response coefficient x^ (2) (-2ω, ω , ω , ω ) over a large frequency range. The electronic linear electro-optic susceptibility x^ (2) (-ω, ω , ω , 0 ) is also evaluated below band gap. These results are based on the series of self-consistent LDA calculations within DFT.