Raman spectra and sensitivity of LLM heterocycles under pressure

The structures of crystals made of two and four molecules of (3,4-bis(3-(4-nitro-1,2,5-oxadiazole-3-yl)-1,2,4-oxadiazole-5-yl)-1,2,5-oxadiazole) were predicted at ambient pressure using evolutionary algorithms and density functional theory (DFT). Thermodynamical, dynamical, and mechanical stabilities of the monoclinic crystals were estimated from ambient pressure to 30 GPa. Elastic moduli of LLM Heterocycle crystals (LLMH) show an abrupt increase between 10 and 20 GPa. Calculations of Raman spectra of the LLMH crystals with a band gap of 2.89 eV at ambient pressure were performed using linear response and variational density functional perturbation theory (DFPT). The density of states at the Fermi level is determined by p-states with the main contribution of N atoms mainly from the rings. The impact sensitivity of the LLMH crystal is rationalized using the up-pumping model. The sensitivity qualitatively estimated from Raman spectra is compared with that of LLM-172 (3,4-bis(4-nitro-1,2,5-oxadiazol-3-yl)-1,2,5-oxadiazole), BDNAPM, and RDX solids.