Pressure-Induced Conformer Modifications and Electronic Structural Changes in 1,3,5-Triamino-2,4,6-trinitrobenzene (TATB) up to 20 GPa

To probe the behavior of structural evolution and optical properties in solid energetic material TATB, X-ray diffraction (XRD) and Raman and absorption spectroscopy were performed under high pressure up to 20 GPa. The absorption edge shifts to red, and the color significantly varies with increasing pressure for TATB. The XRD patterns under high pressure indicate that TATB maintains the triclinic structure within this pressure range. An electronic structural change is observed at ∼5 GPa, resulting from the modification of conformers of TATB, which is associated with the rotation of nitro and amino groups under high pressure. The current experimental results clarified the absence of phase transition below 20 GPa and confirmed that the pressure-induced color change originates from the enhancing conjugation of π orbital due to the shorting C–NO₂ bonds and the rotation of nitro groups with increasing pressure. The third-order Birch–Murnaghan equation of state is obtained up to 16.5 GPa, which is helpful for calculating researchers to verify the correctness of their models.