External electric field induced conformational changes as a buffer to increase the stability of CL-20/HMX cocrystal and its pure components

Abstract

As a significant stimulus, the external electric field (EEF) plays a vital role in affecting the behaviors of energetic materials (EMs). We investigated the effects of the EEF on CL-20/HMX cocrystal and its pure components by molecular dynamics simulations. The COMPASS force field, atom-based summation method for van der Waals interactions, and Ewald summation method for electrostatic forces were applied. The results show that there exists sudden conformational changes at the EEF intensity of 0.3 and 0.9 V/Å for β-HMX and ε-CL-20, respectively, while the EEF-induced conformational change in CL-20/HMX is a gradual process. The analysis of the N-NO2 bond length distributions, radial distribution functions (RDFs) of the intermolecular O⋯H atom pair, and cohesive energy density (CED) reveals that the EEF can remarkably decrease the N-NO2 bond length and enhance hydrogen bonding interactions in the systems. A comprehensive analysis of the structural stability based on the maximum bond length of the trigger bond (Lmax), the interaction energy between two N atoms of the NN trigger bond (EN-N), and mechanical properties indicates that EEF can effectively improve the stability of the systems. These findings provide basic insights into the comprehensive understanding of the effects of the EEF on the EMs.