采用从头算方法以 6 31G 基组对XSO2 NCO(X =F ,Cl)分子的振动谐性力场和红外光谱进行了研究 .由最小二乘法通过拟合FSO2 NCO分子的理论和实验频率优化了一套力常数校正因子 ,然后将其迁移到ClSO2 NCO分子中 ,以产生一个纯理论预测的振动基频 .利用校正后的力场计算得到FSO2 NCO和ClSO2 NCO的振动频率 ,与实验值比较平均偏差分别为 3cm-1和 5cm-1.根据用校正后力场进行简正坐标分析得到的势能分布 (PED)和从头算红外光谱强度值对此二分子的振动基频的指认进行了讨论 . The vibrational harmonic force field and infrared spectra of XSO2 NCO (X = F, Cl) molecule were studied by ab initio method based on the 631G basis set. The theoretical and experimental frequencies of FSO NCO molecules were optimized by least square method A set of force constant correction factors is then migrated into the ClSO2 NCO molecule to generate a purely theoretical vibrational fundamental frequency.The vibrational frequencies of FSO2 NCO and ClSO2 NCO are calculated using the corrected force field and averaged from the experimental values The deviations are 3cm-1 and 5cm-1, respectively. Based on the potential energy distribution (PED) obtained from the orthorectified force field and the ab initio infrared spectral intensity value, the vibration fundamental frequencies of these two molecules are discussed.