Theoretical Study On The Structures And Proper Properties Of The Isomers Of N₆H₆ And N_n(CH)_6-nH₆(n=0～5)

The stabilities and properties on energetic material N₆H₆ have beenstudied by Gaussisn98 program. The contents which are studied in this thesis are asfollows:1. Theoretical study on the structures and stabilities of the chain and ring isomers ofN₆H₆.2. Theoretical study on the structures and stabilities of the chain and ring isomers ofN_n(CH)_6-nH₆(n=0-5)Possible isomers and their tautomerisms on energetic material N₆H₆ are optimized by density function theory (DFT). The calculations are perforned by B3LYP/6-311++G(d,p) basis set. Simultaneously, a series of new N_n(CH)_6-nH₆(n=0-5) molecules are obtained by successive replacement of N atoms with CH groups in a relatively stable configuration of the N₆H₆ chain and ring isomers. For each species, the analyses of vibration are performed to obtain the zero point vibrational energies (ZPE) and to verify whether it is a minimum or not. Meanwhile, the electronic charge densities of critical points were calculated with AIM 2000 program package. Furthermore, the orbital interaction is analyzed with the natural bond orbital (NBO) theory. In addition, G3MP2 method is used to obtain more accurate energy and calculate the HOF at 298 K (â–³_fH^θ(298K)). All calculations are carried out by using the Gaussian 98 program. The results of studies indicate that, the stability of chain-N₈H₈ is higher than ring-N₆H₆, the formation heats of chain-N₆H₆ is less than ring-N₆H₆ The structures and relative stabilities are studied. Energies and heats of formation are calculated by B3LYP and G3B3 method. The results show that heats of formation of all the isomers are positive. The heats of formation of A2-3 is the lowest and C2 is the highest In addition, Energy and heats of formation of ring isomers are greater than those of chain isomers. In the ring isomers, the four-member-ring isomers are the highest and five-member-rings are lowest. Only chair conformation of six-member-ring isomers is existed. The isomers of the chain N₆H₆ which involve N=N are found more stable.Simultaneously ,our research results show that the stabilities of the isomers will reduce with the increment of the number of the -CH-groups to replace nitrogen atoms; the heats of formation of the N_n(CH)_6-nH₆ molecules decrease along with the replacement of nitrogen atoms by -CH- groups.