Theoretical investigation of the second hyperpolarizability of pyrrole homologues C4H4XH (X = N, P, As, and Sb)

Using the results of the three different methods: ab initio HF, MP2 and DFT, the second hyperpolarizabilities of pyrrole homologues were calculated by self-compiling program according to sum-over-state formulae. The calculated results show that as heteroatom atomic number increased, the second hyperpolarizability increased subsequently. Starting from the symmetry, the reasons for the increasing nonlinearity were given by the two-state mold. From the linear relationship of the third nonlinear optical properties between the heteroatom group and the pyrrole homologues, the third nonlinear optical properties were largely determined by the heteroatom. Compared with the optical Kerr effect of the furan homologues, pyrrole homologues are good nonlinear optical materials in application prospect.