Theoretical Study Of The Reaction Mechanism Of The Ap And Hmx, Rdx And Ua Photoisomerization Reaction Dynamics Simulation

The dissertation can be divided into two parts. In One part, we focus on the effects of products of ammonium perchlorate (AP) on the initial pyrolysis of HMX,RDX. In the other part, by using a semiclassical nonadiabatic molecular dynamic simulation-a semiclassical electron-radiation-ion dynamic approach (SERID), we simulating dynamics of the photoisomerization process of urocanic acid.In chapter 1, we briefly show the theoretical background of molecular thermodynamics and molecular dynamics, including the introduction of calculation methods, transition state theory, the frequency calculation and thermodynamic correction, IRC theory, a semiclassical electron-radiation-ion dynamic approach (SERID) methods and the implementation of this program.In the second chapter, we report the effects of NH3,Cl03,NO2,OH and OH- on the initial pyrolysis of HMX. The results indicate that, there are trivial changes on the N-NO2 bond dissociation energies when P-HMX combines with NH3 or ClO3. However, once the complexes decompose, the product NO2 can react with NH3 more easily. This exothermic reaction may induce the subsequent pyrolysis process of HMX. NO2 can easily capture H of the methylene on the HMX ring, which will change the initial pyrolysis channel of HMX. The influence of OH is negligible. The N-NO2 bond dissociation energies of OH- complexes decrease about 200 kJ-mol-1, in comparison with that ofβ-HMX, which indicates that OH- can clearly promote the initial pyrolysis ofβ-HMX. We also obtained bond dissociation energies for N-NO2 in P-HMX and its complexes at Normal Pressure,4 MPa and 6 MPa. The high pressure has no influence on the effects of NH3 and ClO3 on the initial pyrolysis mechanism of HMX.The third chapter describes the effects of H+ on the three kinds of initial pyrolysis of RDX. Our calculation results showed that the H+ can significantly promote the initial thermal decomposition of C-N bond of RDX; We found that H+ induce the RDX to trigger the N-NO2 heterolysis and HONO elimination evidently when H+ approach the N of RDX, which, however, is influenced slightly when H+ approach the O of RDX.In the last chapter, by using a semiclassical electron-radiation-ion dynamic approach (SERID), we study the dynamics of photoisomerization process of urocanic acid. Through the simulation we find that the excited molecule decays to the electronic ground state through different radiationless pathways by given the different photon energy and laser pulses, and the life time of the tracks is also different. Finally, we calculate the potential energy curves with the CASSCF/MRPT2 method.