Chapman-Jouget state

Figure 19 Concentrations at the Chapman-Jouget state of HMX, RDX, and NM using the EXP6 product library.

Next to the - Chapman-Jouget theory, during the last 50 years, the principal methods of calculating detonation pressure and the velocity of flat detonation waves have been the Becker-Kistiakowsky-Wilson (BKW), the Lennard-Jones-Devonshire (LJD) and the Jacobs-Cow-perthwaite-Zwisler (JCZ) equations of state. 

The nature of the Chapman-Jouget and other special thermodynamic states important to energetic materials is strongly influenced by the equation of state of stable detonation products. Cheetah can predict the properties of this state. From these properties and elementary detonation theory the detonation velocity and other performance indicators are computed. Thermodynamic equilibrium is found by balancing chemical potentials, where the chemical potentials of condensed species are just functions of pressure and temperature, while the potentials of gaseous species also depend on concentrations. In order to solve for the chemical potentials, it is necessary to know the pressure-volume relations for species that are important products in detonation... 

We conducted a quantiun-based molecular dynamics simulation of HMX at a density of 1.9 g/cm and temperature of 3500 K for up to 55 picoseconds has been conducted. These are conditions similar to those encountered at the Chapman-Jouget detonation state. Thus, although we do not model the entire shock process, we can provide some insight into the nature of chemical reactivity under similar conditions. Under the simulation conditions HMX was found to be in a highly reactive dense supercritical fluid state. We estimated effective reaction rates for the production of H2O, N2, CO2, and CO to be 0.48,... 

We have applied the present refinements to the EXP6 product library used in Cheetah. With the refined parameters, we can examine the nature of chemical composition at Chapman-Jouget (CJ) detonation states. The CJ states of three common explosives, HMX, RDX, and NM, were determined with the Cheetah program. Results are shown in Figure 19. CH2O is predicted to be present in significant concentrations at the C-J state, but CH3OH is not. 

The theories, developed at the turn of the century by Chapman and Jouget, were refined during the next 50 years and successfully applied to gaseous detonation and then to condensed explosives. With the less-dense, solid organic explosives containing only C, H, N, and O atoms, the theory gave accurate predictions if an appropriate form for the equation of state of the products was... 

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