The first order nonlinear hyperpolarizabilities in second - harmonic generation process and electro - optical pockels effect are computed . the basis set effects in ab - mitio quantum - chemical computation are mainly studied . the correction to the nonlinear optical properties due to the electronic correlation energy is discussed and the relationship between the first order hyperpolarizabilities and the frequencies of the external electric field is also investigated 计算了二次谐波振荡过程和电光pockels效应过程的一阶非线性超极化率，研究了电子的相关能对pna分子的非线性光学性质的影响以及pna分子的一阶非线性超极化率与外加光电场频率之间的色散关系，并着重讨论了量子化学从头计算中基矢组的选取对计算结果的影响。
