High pressure-high temperature decomposition of γ-cyclotrimethylene trinitramine.

Decomposition of γ-cyclotrimethylene trinitramine (γ-RDX) under high pressure-high temperature conditions was examined to elucidate the reactive behavior of RDX crystals. Vibrational spectroscopy measurements were obtained for single crystals in a diamond anvil cell (DAC) at pressures from 6 to 12 GPa and temperatures up to 600 K. Global decomposition rates, activation energies, and activation volumes at several pressures and temperatures below the P-T locus for the γ-RDX decomposition were obtained. Similar to ε-RDX, but in contrast to α-RDX, we found that pressure decelerates the decomposition of γ-RDX. The decomposition deceleration with pressure in the γ-phase can be attributed to pressure-inhibiting bond homolysis step(s). The main decomposition species were identified as N(2)O, CO(2), and H(2)O, in accord with the species reported for the α-phase decomposition at high pressures. This work complements previous studies on RDX at HP-HT conditions and provides comprehensive results on the reactive behavior of γ-RDX; the γ-phase plays a key role in RDX decomposition at P-T conditions relevant to shock wave initiation.