Theoretical studies on the nonlinear optical susceptibilities of 3-methoxy-4-hydroxy-benzaldehyde crystal

Nonlinear optical susceptibilities of a SHG material, 3-methoxy-4-hydroxy-benzaldehyde (MHBA), were investigated at both molecular and crystalline levels, by using the MP2 (second-order level of Møller–Plesset perturbation correction) method and the oriented-gas approximation. The results revealed that the electron donor group –OH and acceptor group –HCO play important roles in the magnitude of second-order polarizabilities. The studies of the oriented-gas model showed the crystal has large nonlinear optical coefficients, d22=23.8d36KDP, d21=13.5d36KDP, d23=29.1d36KDP, d25=12.8d36KDP, which agree well with the experimental results.