本文根据量子力学能量最低原理,以 Hartree-Fock 极限值为标准,通过大量的优选计算,将徐光宪等人提出的改进 STO—3G 从头计算基函数推广到第三周期元素,提出了基组参数α_i、C_i 以及与其匹配的原子轨道指数(?)。并用此基组对第三周期的基态原子和含第三周期元素的典型分子进行了从头计算,各项计算结果明显优于 J.A.Pople 等人提出的 STO—3G 的结果。 According to the principle of lowest energy of quantum mechanics and Hartree-Fock limit, the improved STO-3G basis function proposed by Xu Guangxian et al. Is extended to the third periodic element through a lot of optimization calculations. The basic parameters α_i , C_i and its matching atomic orbital index (?). The ground state atoms of the third period and the typical molecules containing the third period elements are ab initio calculated by this basis set, and the results are obviously superior to the results of STO-3G proposed by J. A. Pople et al.