Accurate determination of pair potentials for a C{sub w}H{sub x}N{sub y}O{sub z} system of molecules: A semiempirical method

Statistical mechanical chemical equilibrium calculations of the properties of high-pressure high-temperature reactive C,H,N,O mixtures are made to derive an accurate self-consistent set of inter-molecular potentials for the product molecules. Previous theoretical efforts to predict such properties relied in part on Corresponding States theory and shock wave data of argon. More recent high-pressure Hugoniot measurements on a number of elements and molecules allow more accurate determination of the potentials of these materials, and explicit inclusion of additional dissociation products. The present discussion briefly reviews the previous analysis and the method used to produce a self-consistent set of potentials from shock data on N{sub 2}, O{sub 2}, H{sub 2}, NO, an N{sub 2} + O{sub 2} mixture, carbon, CO{sub 2}, and CO, as well as some simple explosive product mixtures from detonation of hexanitrobenzene, PETN, and a mixture of hydrazine nitrate, hydrazine and water. The results are tested using the data from an HMX explosive formulations. The effect of the non-equilibrium nature of carbon clusters is estimated using data for TNT as a standard to determine a nonequilibrium equation of state for carbon. The resulting parameter set is used in a survey of 27 explosives. For the subset that contains no fluorine or two-phase carbon effects the rms deviation from experimental detonation velocity is 1.2%