Theoretical computational study of decomposition mechanisms for highly energetic molecule GZT and its derivatives
| Autor: | Sou-Ro Cheng, 鄭淑銣 |
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| Rok vydání: | 2013 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 101 In this thesis, theoretical calculations of decomposition mechanisms and thermodynamic properties for the highly energetic bis(guanidinium) 5,5'-azotetrazolate (GZT) ; and the geometry optimization of the bis(aminoguanidinium) 5,5'-azotetrazolate (AGZT) of GZT derivatives, were investigated. Base on the calculation results of ionic type decomposition patterns, GZT was initially cracked into two guanidinium cations (G+) and a 5,5'–azotetrazolate anion (ZT2-). Three routes－the elimination of a hydronium ion (H+), the elimination of a hydrogen radical (H•), and the elimination of an amino radical (•NH2)－were suggested for the decomposition of the G+ cation. The other three routes－single ring opening, double ring opening, and N–N bond cleavage of outside the ring－were proposed for the further decomposition of the ZT2- anion. Fourteen decomposition species were obtained on splitting both the cation and anion, and also successfully identified 11 G+ cation-related and 11 ZT2- anion-related decomposition transition states. In G+ cation cracking, the lowest activation energy of about 210 kJmol-1 was required, and the final products CN+ and NH3 were obtained. In ZT2- anion cracking, the lowest activation energy of about 250 kJmol-1 was required, and the final products CN– and N2 were obtained. Base on the calculation results of molecular type decomposition patterns, GZT was initiated by heterocyclic ring opening, sequential cracking of the two five-membered rings of GZT, and simultaneous release of N2 molecules; whereas proton transfer, bond-breaking, and atomic rearrangements were performed subsequently. Finally, fifteen reaction paths and five transition states were obtained. The results revealed that (1) the maximum activation energy required is 187.8 kJmol-1, and the enthalpy change (ΔH) and Gibbs free-energy change (ΔG) of the net reaction are −525.1 kJmol-1 and −935.6 kJmol-1, respectively; (2) GZT can release large amounts of energy, the main contribution being from the disintegration of the 5,5'-azotetrazolate anion (ZT2−) skeleton (ΔH=−598.3 kJmol-1); and (3) the final products contained major amounts of N2 gas, but remaining gas molecules such as HCN and NH3 were obtained. The geometry optimization of bis(aminoguanidinium) 5,5'-azotetrazolate (AGZT) of GZT derivatives was studied. The results of calculation revealed that ten stable conformers with different potential energy were obtained, and conformers were named as A1 to A10, respectively, by the order of its energy level from low to high. By using the semi-empirical INDO program “local bond population analysis” method to calculate the intramolecular hydrogen bonding, bond energy, bond order, and Columbic attraction energy of AGZT and its conformers. It can be used to explain the influences of intramolecular hydrogen bonding on the stability of AGZT conformers. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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