Molecular conformational stability in cyclotrimethylene trinitramine crystals

The cyclotrimethylene trinitramine (RDX) molecule has four conformations denoted as Caaa, Caae, Caee, and Ceee, of which Caae is the conformer stabilized at room temperature in the alpha-RDX crystal subjected to atmospheric pressure. The barriers for transition between these conformers are evaluated using a molecular model both in vacuum and in the crystal. Apart from Caae, the only conformer stabilized in alpha-RDX is Caee and this occurs when the crystal is strained. The concentration of Caee depends on strain and temperature. The conformers interact elastically and electrostatically, which leads to their spatial clustering. Furthermore, the transition between Caae and Caee is a stochastic process characterized by temporal correlations. This is an effect of the field-mediated spatial interaction of conformers. It is observed that fluctuations in the intra-molecular effective temperature correlate with conformation transitions. The effect is quantified for both Caae-Caee and Caee-Caae transitions. (C) 2011 American Institute of Physics. [doi:10.1063/1.3609769]