First-principles study of the high-pressure behavior of solid 1,7-diamino-1,7-dinitrimino-2,4,6-trinitro-2,4,6-triazaheptane

The structural, electronic, and absorption properties of crystalline 1,7-diamino-1,7-dinitrimino-2,4,6-trinitro-2,4,6-triazaheptane (APX) in the pressure range of 0–20 GPa have been studied by using density functional theory. A comprehensive analysis of the variation trends of the lattice constants, bond lengths, bond angles, and intra-molecular H-bonds under compression indicates that there are four structural transformations in APX at 2, 4, 10, and 19 GPa, respectively. Structural transformations occurred at 2 and 10 GPa weaken the H-bonding. The impact sensitivity for APX becomes more and more sensitive with the increment of pressure. An analysis of density of states suggests that the band splitting and dispersion increase due to the enhanced intermolecular interactions at high pressures. APX has relatively high optical activity at high pressure. The structural transformation at 4 GPa makes the absorption coefficient of the C–H stretching increase significantly, but the transformations at 2 and 19 GPa decrease that slightly.