中文摘要：

在B3P86／cc—PVTZ水平上，对N2O异构体进行优化计算，得出N2O基态的单重态能量最低，其稳定构型为C∞v构型，平衡核间距R1=0．1121nm，R2=0．1177nm，a=180°，能量为-185．1188a．u．同时计算出基态的简正振动频率ω1（Ⅱ）=601．5010cm^-1，ω2（∑g）=1295．8518cm^-1和ω3（∑u）=2287．0627cm^-1．在此基础上，使用多体项展式理论方法，导出N2O分子的全空间解析势能函数，该势能函数准确再现了N2O（C∞v）平衡结构．

英文摘要：

The equilibrium geometry of N2O, NO and N2 molecules have been calculated on the computational levels of density functional theory. The Murrell-Sorbie analytic potential energy function of NO and N2 molecules have been derived through the least-square fitting to ab initio data. Similarly, the harmonic frequency has been calculated and the analytic potential energy function of linear molecule N2O isomer is derived by many-body expansion theory for the first time.