Understanding the Effect of Solvent on the Growth and Crystal Morphology of MTNP/CL‐20 Cocrystal Explosive: Experimental and Theoretical Studies

Abstract

Abstract The cocrystal of 1‐methyl‐3,4,5‐trinitro‐1H‐pyrazole (MTNP) and 2,4,6,8,10,12‐hexanitrohexaazaisowurtzitane (CL‐20) is prepared in ethanol and investigated through molecular dynamic and quantum chemistry methods. In order to study the solvent effect on the growth and crystal morphology of the cocrystal, MTNP/CL‐20‐solvent and MTNP/CL‐20‐solution interfacial models are constructed and simulated at temperatures ranging from 293 to 323 K. The analyses of polarity and absorption energy show that ethanol molecules have a larger influence on (0 ‐2 0) and (0 2 0) growth surfaces than other faces at each temperature and the predicting and experimental crystal morphologies are similar. By analyzing the binding energy of MTNP/CL‐20‐solution models, it is clear that MTNP and CL‐20 molecules are easier to be adsorbed on the growth surfaces than ethanol in the solution, and the results of cooperativity effect show that the MTNP binding to CL‐20 is tighter in the presence of ethanol. Those are perhaps the reasons why crystals with good quality were obtained from the ethanol solvent.