Quantum Chemistry Investigation On Nitrogen Clusters And Blue-Shifting Hydrogen Bond Systems

In this work,ab initio investigations have been carried out to examine odd-number nitrogen clusters with low spin. Six Ns,five V four NS- ,nine N?,four N7+. six N7- are reported for the first time. All of them are identified as local minima on the MP2(FU)/6-31 G(d) potential energy surfaces. The most stable NS radical. N5+ cation. N5- anion are the structure 1 (Cj 7 (Cr). 12- (CV),respectively. The most stable N7 radical,N7+ cation,N7- anion are the structure I (Cs) r (CV 5- (C1),respectively. Based on NBO analysis,their bondings are discussed. Comparing the even-number nitrogen clusters with the odd-number nitrogen clusters,we find many differences between them. Such as,the structures that are gotten at the MP2 level are much different from those at the B3LYP level. The bond lengths and bond angels change greatly. Some structures are local minima at the MP2 energy surfaces. But at the B3LYP level,they may be saddle-points. The bondings of the odd-number nitrogen clusters are also very complicated. The single-electron bonds appear in some structures. Some non-classical structures are found. The stability of some of the more stable isomers is enhanced by conjugation or hyperconjugation. According to our research,we know more about the odd-number nitrogen clusters. This work also further testifies the possibility that the odd-number nitrogen clusters are likely to be stable and become the high-energy density materials potentially if they could be synthesized.Ab initio quantum mechanics methods are applied to investigate the CH-N mtermolecular interactions between ammonia and halomethanes. A new type of improper blue-shifting hydrogen bonds (CH--N blue-shifting hydrogen bonds) areidentified in NHrH3X(X= F,Cl,Br,I) complexes,which provide blue shift of about 11-26 cm-1. For NH3--CHX3 (X= F,Cl,Br,I) complexes,stronger hydrogen bonds come into being,but they are all classical hydrogen bonds,which provide red shift of about 94-183 cm-1. The NBO analyses explain why blue shift and red shift happen in different halomethanes successfully. The different ways of electron density transferred for interactions of NH3--CH3X and NH3-CHXs result in that blue shift for NH3-CH3X,red shift for NH3-CHX3.