Non-equilibrium molecular dynamics study of interfacial phonon transport in energetic materials: Coherent transport of acoustic phonon and NN stretching at bicrystal RDX interface

Interfacial phonon transport poses a fundamental challenge for understanding energy transfer in energetic materials. We investigated interfacial phonon transport behavior in bicrystal cyclotrimethylene trinitramine using non-equilibrium molecular dynamics simulation under both thermal excitation and mode-selective coherent phonon pulse excitation. Time- and spatial- resolved spectral analysis were combined to reveal the phonon scattering mechanisms. For thermal excitation, internal vibrational modes around 1500 cm −1 were found to play a fundamental role in single crystal, whereas the low-frequency phonons below 100 cm −1 exhibit higher transmission efficiency and a faster response across the bicrystal interface. Wavelike coherent transport across the interface was observed for both acoustic phonons and N N stretch mode near 1600 cm −1 . The high group velocity of acoustic phonons was identified as a key factor enabling them to propagate across the interface ballistically. For the N N stretching vibration, its weak anharmonic coupling with other vibrational modes and favorable structural matching at the interface facilitated its coherent interfacial transmission, together with a rapid interfacial energy localization. Our findings provide valuable insight into energy transfer and initiation mechanisms in energetic materials.