Journal
JOURNAL OF PHYSICAL CHEMISTRY A
Volume 124, Issue 50, Pages 10580-10591Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpca.0c09463
Keywords
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Funding
- U.S. Department of Energy by Lawrence Livermore National Laboratory [DE-AC52-07NA27344]
- LLNL LDRD program [18-SI-004]
- high explosives Dynamic Materials Properties research program at LLNL
- DOE Office of Science by Argonne National Laboratory [DE-AC02-06CH11357]
- COMPRES under NSF [EAR-1606856]
- GSECARS through NSF [EAR-1634415]
- DOE [DE-FG02-94ER14466]
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The high-pressure equation of state (EOS) of energetic materials (EMs) is important for continuum and mesoscale models of detonation performance and initiation safety. Obtaining a high-fidelity EOS of the insensitive EM 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) has proven to be difficult because of challenges in experimental characterization at high pressures (HPs). In this work, powder X-ray diffraction patterns were fitted using the recently discovered monoclinic I2/a phase above 4 GPa, which shows that TATB is less compressible than when indexed with the triclinic P (1) over bar phase. First-principles calculations were performed with Perdew-Burke-Ernzerhof (PBE) and PBE0 functionals including thermal effects using the P (1) over bar phase. PBE0 improves the description of hydrogen bonding and thus predicts accurate planar a and b lattice parameters under ambient conditions. However, discrepancies in the predicted lattice parameters above 4-10 GPa compared with experimental measurements indexed with P (1) over bar are further evidence of a structural modification at high pressure. Layer sliding defects are formed during molecular dynamics simulations, which induces an anharmonic effect on the thermal expansion of the c lattice parameter. In short, the results provide several insights into determining high-fidelity EOS parameters for TATB and other molecular crystals.
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