Effect of temperature and hydrostatic pressure on the Raman active internal and external modes of 1,3,5-trinitro-1,3,5-triazocyclohexane

The effect of temperature and hydrostatic pressure up to 30 kbars on the Raman active internal and external vibrational modes of solid 1,3,5-trinitro-1,3,5-triazocyclohexane has been measured. Mode Grüneisen parameters have been calculated. The effect of pressure and temperature on the mode frequencies have allowed a separation of the implicit and explicit contributions to the temperature dependence of the vibrational frequencies of the lattice modes. The results indicate an unusually large explicit contribution for a molecular crystal, suggestive of covalent bonding between the molecules of the lattice. The CH₂ symmetric stretching vibration of the molecule showed an atypically large pressure dependence for an internal molecular mode, having a slope 30% larger than the most pressure dependent lattice mode.