Raman Spectra and Sensitivity of LLM-210 under Pressure.

Vibrational spectra of LLM-210 (3,4-bis(3-(4-nitro-1,2,5-oxadiazole-3-yl)-1,2,4- oxadiazole-5-yl)-1,2,5-oxadiazole) solids were studied experimentally and theoretically at high pressures. Calculations of LLM-210 crystal with band gap of 2.88 eV at ambient pressure and 2.55 eV at 10 GPa were performed using linear response and variational density functional perturbation theory (DFPT). Density of states at Fermi level is determined mainly by p-states of nitrogen and oxygen atoms with the main contribution of N atoms from the rings and O atoms from NO2 groups. Impact sensitivity of llm210 crystal is rationalized from calculation of the low frequency vibrational modes. The doorway frequency modes are responsible for energy transfer from a shock wave to the molecules of a crystal. Particularly the difference between the lowest doorway mode and the highest external mode correlates with impact sensitivity. The sensitivity is compared with DFPT Raman calculations of LLM-172 (3,4-bis(4-nitro-1,2,5- oxadiazol-3-yl)-1,2,5-oxadiazole) and RDX solids.