Internal standard-assisted ab initio MD simulation for comparative thermal stability and decomposition mechanisms of energetic materials

Thermal stability is one of the most important and fundamental properties of energetic molecules, and still suffers from many challenges in theoretical evaluation prior to experiment determination. This work introduces a novel strategy combining an internal standard method with ab initio molecular dynamics (MD) simulations to overcome the challenges. The proposed approach is validated using five pairs of energetic molecules with different molecular structures and experimental thermal stability. That is, in MD simulations, the molecule that decomposes first with higher frequency in each pair always corresponds to a lower decomposition barrier. This strategy can overcome the issues of the serious temperature fluctuations in ab initio MD simulations, the significant dependence of molecular reaction MD simulation on force field accuracy, and empirical speculation or tedious trial-and-error deduction of thermal decomposition mechanism in static QC calculations. Therefore, it will facilitate to more accurate prediction of thermal stability and decomposition mechanisms of energetic molecules, in particular for those that have not been synthesized yet. A novel approach is introduced for evaluating the comparative thermal stability and decomposition mechanisms of energetic materials using internal standard-assisted ab initio molecular dynamics (MD) simulations. The workflow involves selecting both an object molecule and a reference molecule, and subjecting them to parallel MD simulations. The resulting decomposition events are analyzed and compared, providing mechanistic insights into the relative stability of different energetic compounds. This strategy enables rapid, visual, and reliable assessment of thermal stability, overcomes common challenges in theoretical predictions, and supports the rational design of safer, more stable energetic materials. • A novel internal standard-assisted ab initio MD to assess thermal stability and decomposition in energetic materials. • The approach enables intuitive comparisons across molecule pairs and mitigates temperature fluctuations and empirical limits. • The method is validated on five energetic pairs, demonstrating its potential for prediction and mechanism insight.