C-H,C-N,C-O,N-N的键离解能和键长的计算

Calculations of bond dissociation energies and bond lengths of C-H,C-N,C-O,N-N

用B3LYP/6-311G**和CCSD/cc-pVDZ方法对CH4、CH3、CN、CO、N2、CH3NH2、CH3NO2、NH2NO2八个分子中的C-H、C-N、C-O、N-N键离解能进行计算,通过比较研究可知,计算CH3、CH3NH2、CH3NO2分子中的C-H键离解能和CN、CO、N2分子的键离解能用B3LYP/6-311G**方法可靠,而计算CH3-H、CH3-NH2、CH3-NO2和NH2-NO2分子的键离解能用CCSD/cc-pVDZ方法更可信;用以上二种方法对本文的八个分子的平衡几何结构进行优化求出所需的键长,通过比较可知,CH4、CH3、CN、CO、N2分子用B3LYP/6-311G**的方法进行平衡几何优化求得的键长更可靠,而CH3NO2、NH2NO2、CH3NH2分子则用CCSD/cc-pVDZ方法优化出的键长是更可信.

The bond dissociation energies of C - H, C- N, C- O, N - N for eight molecules of CH4、CH3、 CN、CO、N2、CH3NH2、CH3NO2、NH2NO2 are computed using the levels of B3LYP/6-311G^＊＊ and CCSD/cc - pVDZ. By comparison, the B3LYP/6 - 31G^＊＊ is found to give the best results of C - H bond dissociation energies for CH3、CH3NH2 、CHaNO2 molecules and C - N,C - O、N - N bond dissociation energies of CN、CO、 N2 molecules. And then the CCSD/cc- pVDZ is the most reliable method for the evaluation of the bond dissociation energies of CH3 - H、 CH3 - NH2、 CH3 - NO2、 NH2 - NO2 molecules. The equilibrium geometries of the eight molecular systems are optimized to compute their bond lengths using the above same way, It is noticed that the B3LYP/6 - 31G^＊＊ is showed to obtain the best results of bond lengths of CH4、CH3、CN、 CO、N2 molecules, the CCSD/cc - pVDZ is believed to get more reliable the bond lengths of CH3NO2、NH2NO2、CH3NH2 molecules.