Searching for the optimal molar ratio of CL-20/FOX-7 cocrystal via evolutionary algorithm and machine learning

In this work, we report the discovery of the most stable cocrystal molar ratio and structure for CL-20/FOX-7 compounds through an innovative workflow integration evolutionary algorithm with machine learning potential. 2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), currently the most powerful industrial explosive, is limited in its applications due to its high mechanical sensitivity. Cocrystal engineering with traditional energetic materials like 1,1-diamino-2,2-dinitroethylene (FOX-7), which exhibits low sensitivity and high energy density comparable to hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), has been proposed to address this limitation. Using our computational framework, thousands of high-density cocrystal structures with ratios spanning 4:1 to 1:6 were generated. Subsequent density functional theory with dispersion corrections (DFT-D3) screening identified several optimal configurations exhibiting both high density and low binding energy. The findings reveal that the 1:1 molar ratio configuration achieves the maximum density of 1.934 , while molar ratios 1:1, 1:2, 1:3, and 1:6 have a higher average binding energy. The 1:1 and 1:2 molar ratios have the lower formation enthalpy Q . One notable structure is K1705 with a molar ratio of 1:2, which has the largest bonding energy and can form a comparatively strong hydrogen bond net structure. 1. An evolutionary algorithm coupled with machine learning potential has been employed to investigate the CL-20/FOX-7 cocrystal configuration space. 2. The PBE-D3 method, which has improved performance on molecular cocrystals, is used to verify the cocrystal structures generated by the search flow. 3. In this study, we explored molecular cocrystal structures featuring hydrogen bond networks. For the cocrystals that we searched and experimentally synthesized, the binding energy, entropy of formation, and hydrogen bond energy are calculated to provide a direct characterization of their structural stability.