Abstract: The dipole moment(μ), polarizability(α) and the first hyperpolarizability(β) of van der Waals complexes anion [Li…X]e-[1](X=FH, OH2, NH3) were calculated by using ab initio methods with 6-311G basis set series at MP2 level. We also discussed the contribution of the effect of basis set and the electronic correlation on the dipole moment, polarizability and the first hyperpolarizability, and compared the contributions of valence electrons to the first hyperpolarizability. The values of dipole moment, polarizability and the first hyperpolarizability of three complexes anion calculated with MP4(SDQ)/6-311++G(2df, 2pd) are: μ=2.5633 a.u., α=1.0476×10³ a.u., β=1.0948×10⁵ a.u. for [Li…FH]e-[1], μ=2.3204 a.u., α=1.2201×10³ a.u., β=2.1410×10⁵ a.u. for [Li…OH2]e-[1] and μ=2.4687 a.u., α=1.4817×10³ a.u., β= 3.4040×10⁵ a.u. for [Li…NH3]e-[1], respectively. The results showed that all the three complexes anion had huge first hyperpolarizability, andthe contributionof one valence electron tothe first hyperpolarizabilitywasmore than1.0×10⁵ a.u..

Key words: Nonlinear optics, The first hyperpolarizability, Ab initio, [Li…X]e-[1](X=FH, OH2, NH3), HOMO