Exploring the effects of solvents on an organic explosive: Insights from the electron structure, electrostatic potential, and conformational transformations of 2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane

In order to attain comprehensive insights into the crystallization of 2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane (CL‐20) from solutions, the geometric and electronic structures and conformational transformations of its β‐, γ‐, ε‐, ζ‐ and η‐ forms in six organic solvents (ethanol, ethyl acetate, methanol, acetone, acetonitrile, and 2‐propanol) were evaluated using quantum chemistry calculations. Results showed that solvents have little effect on the geometric structures of molecules but greatly impact the energy and electronic structure of CL‐20. The electron density, atomic charges, and electrostatic potential of CL‐20 exhibit polarization due to the solvent effect, especially in alcohols. The polarity of CL‐20 increased because of the change in electron density. The transformations of the five conformers of CL‐20 were studied thoroughly, and the energy barriers were evaluated using the Gibbs energies. Importantly, the reason η‐CL‐20 is only found in CL‐20‐based cocrystals was suggested. These results indicate that solvents play a critical role in crystal growth. The geometric and electronic structures and energy features of CL‐20 polymorphs, as well as their transitions of molecular conformers in gas and solvents, were investigated thoroughly using quantum chemistry methods. The molecular behaviors of CL‐20 in a solvent were given in detail in order to study the effects of solvents on an organic energetic molecule. These findings will be useful for understanding the crystallization of energetic materials from solutions.