Alleviating the stability-performance contradiction of cage-like high-energy-density materials by a backbone-collapse and branch-heterolysis competition mechanism

Searching for advanced strategies to alleviate the inherent contradiction between stability and performance has been one of the most challenging tasks in the development of high-energy-density materials (HEDMs) for centuries. Recently, our high-throughput calculations and machine learning studies showed that cage-like HEDMs have a high probability of owning simultaneous high thermostability and high performance. To explore the physical mechanism of the data-driven prediction, quantum mechanical molecular dynamics simulations were carried out to study the early thermolysis of a series of caged HEDMs at the crystal level. Herein, an interesting competitive process between backbone-collapse and branch-heterolysis was discovered, and the process was found to significantly relate to the temperature and isotropy degree of the cage-like conformation. In the simulated storage or transport temperature range, branch-heterolysis is the predominating process. The highly isotropic cage-like conformation can delay the onset time of HEDMs, providing the reactant molecules with extra stability to suppress successive decomposition. However, in the simulated explosion temperature range, the backbone-collapse became dominant. A considerable scope of reactant molecules was initiated through backbone-collapse, which deteriorated the thermostability of the caged HEDMs and accelerated their energy release, endowing them with higher performance. The current research demonstrates cage-like conformations in alleviating the stability-performance contradiction of HEDMs and provides a theoretical guide for the rational design of novel advanced compounds.