Solid‐Solid Phase Transformation Behavior of <i>ϵ</i>‐CL‐20 Induced by Typical Organic Solvents: A Theoretical and Experimental Study

Abstract The solid‐solid phase transformation of ϵ ‐CL‐20 induced by external conditions is one of the bottlenecks limiting the widespread applications of CL‐20‐based energetic materials. Herein, we report the investigation on the influence of solvent polarity on ϵ ‐CL‐20 solid‐solid phase transformation behavior both theoretically and experimentally. Density functional theory (DFT) calculation was performed to evaluate the possibility of ϵ ‐CL‐20 phase transformation induced by organic solvent molecules from the perspective of ϵ ‐CL‐20 electronic structure and molecular structure variations. Additionally, experimental study of ϵ ‐CL‐20 phase transformation induced by 1,2‐dichloroethane, ethanol, and methanol gas environment was conducted. Solvent with higher polarity was confirmed to significantly vary molecular surface electrostatic potential and molecular conformation of ϵ ‐CL‐20 molecule. Furthermore, ϵ ‐CL‐20 critical phase transformation temperature decreased when using inducing solvent with higher polarity. And the observed maximum phase transformation rate was the one induced by the highest polarity solvent. A four‐parameter model was established to describe the phase transformation process as a function of time based on the experimental results. Possible ϵ ‐CL‐20 solid‐solid phase transformation mechanism was proposed. Hopefully, these results will be beneficial for the rational preparation and utilization of CL‐20‐based energetic materials.