Stability of LLM-172 under high pressure


LLM-172 or 3, 4-bis (4-nitro-1,2,5-oxadiazol-3-yl)-1,2,5-oxadiazole has been studied experimentally and computationally modeled at high-pressure. Minimum enthalpy structures were relaxed using norm-conserving pseudo potentials which provided a high level of convergence for the final computational structures. The calculated P-V curve fits reasonably well to the experimental X-ray diffraction data. No phase transitions or deviations from the P212121 (D2-4) space group of the LLM-172 crystal were observed to near 35 GPa, although slight modifications to the molecular geometry were noted in the Raman spectra. Density functional perturbation theory was used to obtain calculated Raman spectra; these calculated spectra were then used for comparison with experimental Raman spectra and the identification of the atomic motions associated with the vibrational modes. Based upon the modification of the experimental Raman spectra with pressure potential decomposition mechanisms are proposed. Quantum mechanical molecular dynamics (QM MD) calculations of LLM-172 surfaces resulted in determination of the very first fragments decomposed from the surface at high temperatures.

Publication Title

AIP Conference Proceedings