Effect of solvent mixture on the formation of CL-20/HMX cocrystal explosives.

2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20)/1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX) cocrystal is widely concerned due to its high safety and low sensitivity. A CL-20/HMX-solution interface model was constructed to investigate the effect of solvent mixture on cocrystal morphology. The interface models of different solvent mixtures were simulated by molecular dynamics (MD) and quantum chemistry (QC) methods at room temperature. The analyses of binding energy show that CL-20 and HMX molecules are easier to be adsorbed on the cocrystal surface in the presence of solvent mixture dimethyl sulfoxide (DMSO)/acetonitrile (ACN). Mass density distribution and diffusion coefficient analyses demonstrated that the growth of CL-20/HMX cocrystal will be freer in DMSO/ACN. Cooperativity effect analysis shows that the CL-20 binding to HMX is tighter in the presence of DMSO/ACN and the system is more stable. Our findings may provide some guidelines for preparing cocrystal in solvent mixture. Graphical abstract.