中文摘要：

利用密度泛函理论的B3LYP杂化方法,在相对论有效芯势模型下,使用Gaussian 03程序对IV价镎离子（Np^4＋）与硝酸根离子（NO3^-）形成的几种配合物Np（NO3）_n-q（n=1-6,q=-2-＋3）的几何结构进行了优化,给出了其结构参数及性质.研究发现：Np^4＋与NO3^-在结合过程中均以双齿模式结合,且Np^4＋与2（NO3^-）结合形成的Np（NO3）2^2＋配合物的Np—N键及Np—O键的键长最短,但Np^4＋与4（NO3^-）结合形成的Np（NO3）4配合物的结合能最大、结合最稳定.最后,进一步计算了Np（NO3）4配合物的红外光谱,通过与已有的实验数据对比的一致性,确认了本文计算结果的可靠性.

英文摘要：

In the process of nuclear waste disposal,the valuable uranium and plutonium are recycled and separated by dissolving the spent fuel in nitric acid.However,transuranic Np greatly influences the process of separation and recovery.Therefore,it is vital to study the structure and properties of nitrate,which is combined with neptunium ions and nitric acid.Furthermore,there are few researches about nitrate formed by tetravalent neptunium ions.So in this article,by using B3 LYP hybrid method of density functional theory,the Gaussian 03 program is used to optimize the geometric construction of the coordination compounds Np（NO3）n-q （n = 1–6,q =-2–＋3） formed by the tetravalent neptunium ions（Np^4＋） and nitrate ion（NO3^-）.Under the relativistic effective core potential model,the structure parameters and properties are reported.It is found that NO3^-coordinates to Np^4＋ as a bidentate ligand,and the Np—N and Np—O bonds are the shortest in Np（NO3）2^2＋,while the binding energy of the Np（NO3）4 is the largest.The infrared spectra of Np（NO3）4 are calculated in the gas and liquid phase.Comparing with the available experimental data,the reliability of the calculation results in this work is confirmed.