Studies On The Structures And Properties Of Heterocyclic Nitramine High Energy Compounds And Related Mixtures

Heterocyclic nitramine RDX (cyclotrimethylene trinitramine) and HMX (cyclotetramethylene tetranitramine) are high explosives widely used with better comprehensive properties. In this dissertation, by applying the theories of modern quantum chemistry, molecular mechanics and molecular dynamics, systematic computation and simulation are carried out to RDX, HMX and their homologous compounds, RDX dimer, their supermolecules respectively with CH4, CF4 and PbO, especially to polymer bonded explosives (PBXs) composed of HMX and a series of fluorine-containing polymers. Important progression and creative results are obtained in exploring the regular relations between structures and properties.1. With density functional theory (DFT) method at the B3LYP/6-31G* level, the molecular geometries, electronic structures and IR spectra of RDX and HMX are calculated and investigated. Thermodynamic properties such as entropies, enthalpies and specific heats at the temperature 300K-1200K are obtained via the computation based on statistical thermodynamics. The resultant molecular geometries and major IR characterization frequencies are in good agreement with experimental results.2. The molecular geometries and electronic structures, IR spectra and thermodynamic properties of tetracyclic nitramine decacyclic nitramine are predicted using density functional theory (DFT) method at the B3LYP/6-31G** level. The comparison with the corresponding results of hexacycle RDX and octacycle HMX shows that the structures and properties of the four compounds change regularly and their stability decreases with the increasing cycle size.3. Based on the full optimization geometries of a series of heterocyclic nitramines at B3LYP/G-31G** level, the molecular volumes and theoretical densities are calculated on 0.001e/Bohr3 electron density space with Monte Carlo method. Also their heats of formation are obtained by the computation. Further their detonation velocities and pressures are calculated with Kamlet formulae. It is found that the detonation velocity and pressure increase with the increasing cycle size.4. The supermolecular structure of RDX dimer is obtained with ab initio method at HF/6-31G* level by using RDX crystal experimental values as initial geometry. The molecular interaction energy of is obtained via basis set superposition errors (BSSE) correction and MP2 electron correlation energy correction. The interaction essence of molecules is revealed by natural bond orbital (NBO) analysis.5. Due to the requirement of considering the groups frequently seen in general polymers and fluorine-containing polymers, the interactions between RDX, HMX and CH4 and CF4 are studied with ab initio method at HF/6-31G* level, and the interaction essence is explored by NBO analysis.6. PbO is an important promotion agent in the propellent. With ab initio method at HF/sdd level, the complex of HMX and PbO is calculated. NBO analysis indicates that only oxygen atom in PbO interacts directly with HMX octacycle.7. By using semi-empirical AMI, PM3 MO methods and PCFF, COMPASS force fields MM methods, the interactions between HMX and a series of polymers are calculated with the atomic cluster model of dimension match. The binding energies obtained by the four methods are linearly correlated well.8. Molecular dynamics (MD) method using COMPASS force field and elastic mechanics fundamental principles have been employed to simulate and investigate the mechanical properties of pure HMX crystal and its PBXs, i.e. HMX blended with a series of fluorine-containing polymers (Poly(vinylidene difluoride) Polychlorotrifiuoroethylene F2311, F2314). It is found that the mechanical properties can be improved indeed by blending with fluorine-containing polymers in small amounts.9. By COMPASS force field MD simulation, the elastic coefficients, and the effective isotropic mechanical properties like moduli, Poisson's ratios, and Lame coefficients of pure HMX at the temperature of 245K-495K are obtained. It is found that rigidity decreases and the fle...