Ab initio Study of Nonlinear Optical Properties of Urea

The relations of basis sets and optimized geometries to the ab initio results for the molecular polarizability, first hyperpolarizability and second hyperpolarizability of urea have been studied by coupled-perturbed Hartree-Fork （CPHF）method. The introductions of polarzation and daffuse functions significantly improve the calculation results and the geometries optimized on various levels cause relatively small deviations. The dynamic polarizabilities and hyperpolarizabilities of in in several nonlinear optical processes have also been calculated by time-depended CPHF method.