中文摘要：

利用B3LYP杂化密度泛函方法，在相对论有效芯势模型下，优化得到了NpO2^2＋离子及其配合物在气相和水溶液中的几何结构和电子结构，研究了NO3－、SO2－4和CO2－3离子及其水溶液对NpO2^2＋离子的结构和性质的影响。结果表明，NpO2＋2离子结合各种酸根离子后其Np＝O键的键长都有明显增长、Np和O原子的价电子轨道能均有升高，而考虑溶剂化效应后酸根离子的影响将减小。电荷分析发现，结合酸根离子后，NpO2^2＋中Np和O原子间形成的共价键的强度减弱、键长增长。对NpO2^2＋离子与三种酸根离子的理论结合能的比较显示，NpO2 CO3分子最为稳定。

英文摘要：

The geometries and electronic structures of NpO2^2＋ ions and Neptunyl complexes were obtained by u-sing the relative effective core potential （RECP） at density functional theory （DFT）.The influence of ligands on the structural properties of NpO2^2＋ ions in gaseous and aqueous phases has been discussed .After NpO2＋2 ions binding ligands , Np=O bond length is longer , O=Np=O axial bond is bent , the bond energies from the val-ance orbitals of Np and O are increased .The influence of ligands on the structural properties of NpO2^2＋ ions was reduced after considering solvation effects .Electron density analysis indicates that the overlap between neptunium and the axial two oxygen atoms is diminished with NpO2^2＋ ions binding ligands , as a result , the Np =O axial bond distance is elongated.Finally, according to the calculated binding energies among the three ligands and NpO2^2＋ ions, NpO2 CO3 is found to be the most stable molecule among the three Neptunyl complexes .