The Role of Electron-Phonon Interactions on Electronic Transitions of Molecular Energetic Crystals

Despite recent progress in elucidating electronic and phononic contributions to phase transformations and bond scission in molecular energetic crystals, the role of electron-phonon coupling (EPC) remains elusive. Herein, we investigate electron-phonon interactions in β-HMX under hydrostatic pressure using first-principles density functional theory (DFT) based calculations. The EPC strength is found to vary with pressure, with dominant contributions arising from electrons scattering with optical phonons in the frequency range 667-1334 cm-1 near the Γ-point, primarily associated with N-NO2 bending vibrations. The incorporation of electron-phonon interactions leads to substantial bandgap renormalization up to -478 meV at 400 K and 10 GPa. Pressure further enhances electron lifetimes, suppressing electron-phonon scattering rates and enhancing electrical conductivity and the electronic contribution to thermal conductivity near the band edges. This study provides an alternative framework for providing atomistic insights into the mechanisms that influence the sensitivity of energetic crystals.