Nearly Equivalent Inter- and Intramolecular Hydrogen Bonding in 1,3,5-Triamino-2,4,6-trinitrobenzene at High Pressure

We report density functional theoretical calculations of the equation of state (EOS) of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) under hydrostatic compression of up to 250 GPa. Our results show increasing bond equivalency between the intramolecular and intermolecular hydrogen bonds of the amino and nitro groups in the region 30 < P < 70 GPa, beyond which the difference between the two bond distances remains constant. This approximate bond equivalency is manifested by a rapid decrease of the intermolecular −NO···HN– distance along the b lattice direction from 2.6 Å at the zero pressure equilibrium geometry to 1.72 Å at 67 GPa and by a decrease of the intramolecular −NO···HN– bond from 1.65 to 1.57 Å for the same pressure region. The strengthening of intermolecular hydrogen bonding with increased pressure is in accordance with recent infrared spectroscopic measurements of decreasing activity of NH 2 vibrational modes with increasing pressure up to 40 GPa.