Pressure- and Temperature-Dependent Structural Stability and Photoluminescence properties of LLM-105 Crystal

Energetic material LLM-105 maintains its structure stability under high pressure below 30 GPa at room temperature or in the temperature range from 513 K to 5 K with ambient pressure. One structural phase transition occurs at about 30 GPa and is confirmed by pressure-dependent Raman and infrared spectra.
The structure of LLM-105 crystal shows anisotropic compressibility under pressure. Debye temperature of 1225 K for this crystal is obtained. Raman and infrared spectra at extreme conditions suggest that the structure stability is contributed to the stronger inter- and intra- molecule hydrogen bonding networks within LLM-105 crystal.
Photoluminescence, absorption spectroscopy and the DFT calculations were employed for LLM-105. With the pressure increasing, the luminescence first increases due to the limited molecular vibration, then over 9.0 GPa, the intensity decreases due to the lower electronic transfer efficiency. Results reveal that the band gap of LLM-105 crystal presents a strong pressure dependence. The high pressure phase transition has also been observed at about 30 GPa with a band gap suddenly decrease again.
Moreover, the PV phase diagram has been completed.
[1] Stavrou, E.; et. al., J. Chem. Phys. 2015, 143, 144506.
[2] Manaa, et. al., J. Chem. Phys. 2014, 141, 064702.