HNNH3的从头计算研究

Ab-Inito Study on HNNH_3

Ab-Initio studies applying the 3-21G, 6-31G and 6-31G** basis sets and also including the MP2 correction were carried out on H2NNH2, HNNH3 and the transition state molecule of the reaction H2NNH2=HNNH3. First, the geometry of the three molecules was optimized using the theoretical methods mentioned in the Hartree-Fock(HF) scheme. The energies of the molecules corresponding to RHF/6-31 G** geometries were subsequently calculated including electron correlation effects at the level of the second-order Moller-Plesset(MP2) perturbation theory. The vibrational frequencies, net charges and dipole moments were obtained from the theoretical calculations. The results of our ab-initio calculations indicate unambiguously that H2NNH2 is thermodynamically more stable than HNNH3. On the other hand, an isolated HNNH3 molecule once created would be rather stable since barriers for its unimolecular isomerization and decomposition are relatively high. Nevertheless, HNNH3 can be considered as an intermediate in chemical processes involving N2H4. This assumption has been supported by further calculation at higher level of theory.