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本文报告我们对N_2O_4分子所作的从头计算(ab initio法)和半经验计算(用的是CNDO/2法)。通过计算所获得的结果主要是:(1)半经验的CNDO/2法用于象N_2O_4这样较特殊的分子的计算上一般讲是不适宜的。(2)我们用STO·3G极小基组SCF ab initio计算所得的N_2O_4分子总能量为E(T)=-402.482 au.及内旋转势垒为6.28Kcal-/mol,与文献上同类方法所得结果一致;而比用较大的高斯函数展开(73/73)所得的结果E(T)=-406.378au.的负值要小以及比其所得出的内旋转势垒11.6Kcal/mol要小,但比由实验所作出的内旋转势垒估计值2.9Kcal/mol要大,这表明后者与理论计算值不符。(3)由此我们预计,若用包括氮的3 d的扩展基组abinitio计算将得到比本次计算更好的结果(且会有助于对N_2O_4中N-N长键之分析)。
This paper reports ab initio and semi-empirical calculations (using the CNDO / 2 method) for N 2 O 4 molecules. The results obtained by the calculation are mainly: (1) The semi-empirical CNDO / 2 method is generally unsuitable for the calculation of more specific molecules like N 2 O 4. (2) The total energy of N 2 O 4 molecule calculated by SCO ab initio of STO · 3G minimal group is E (T) = - 402.482 au and the internal rotation barrier is 6.28 Kcal- / mol, which is the same as that of the same method The results obtained were consistent with the results obtained with a larger Gaussian function (73/73). E (T) = - 406.378au. The negative values are smaller and smaller than the derived internal rotation barrier of 11.6 Kcal / mol , But larger than the 2.9Kcal / mol estimated by the experimental internal rotation barrier, indicating that the latter does not match the theoretical calculation. (3) From this we can expect that using the 3-day extension of the abinitio calculation, which includes nitrogen, will yield better results than this one (and will facilitate the analysis of N-N long bonds in N 2 O 4).