Molecular dynamics and first-principles studies of structural change in 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) in crystalline state under high pressure: Comparison of hydrogen bond systems of TATB versus 1,3-diamino-2,4,6-trinitrobenzene (DATB)

摘要

Classical molecular dynamics (MD) calculations were performed to reveal the effect of high pressure on the crystal structure of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), an insensitive energetic material. The primary simulation cell consisted of 54 molecules in a triclinic cell, corresponding to 27 unit cells obtained by replicating the experimentally determined unit cell. Inter- and intra-molecular hydrogen bonds were maintained in the range of 1.0 atm to 20.0 GPa as pressure was incremented by 0.5 GPa. The pressure dependence of the interlayer distances (h(1)) and farthest intermolecular distance (d(1)) between nitro groups in the TATB crystal's unit cell was investigated in the same range. h(1) decreased monotonously from 3.50 to 2.90 A as pressure increased to 20.0 GPa. However, d(1) increased considerably with pressure up to 4.0 GPa, most remarkably between 2.0 and 4.0 GPa. Thus, a unique structural change occurred in TATB crystal in this range. On the other hand, 1,3-diamino-2,4,6-trinitrobenzene (DATB) crystal showed a unique structural change between 7.0 and 8.0 GPa. These discrepancies are attributed to the different network systems of hydrogen bonding of these two molecules. To validate the MD calculation results, we conducted first-principles calculations. MD and first-principles calculations showed good agreement with previous experimental results. (C) 2016 Elsevier B.V. All rights reserved.