Detonation-induced transformation of graphite to hexagonal diamond

Stavrou, Elissaios; Bagge‐Hansen, Michael; Hammons, Joshua A.; Nielsen, Michael H.; Steele, Brad A.; Xiao, Penghao; Kroonblawd, Matthew P.; Nelms, Matthew; Shaw, William L.; Bassett, Will P.; Bastea, Sorin; Lauderbach, Lisa; Hodgin, Ralph; Perez-Marty, Nicholas; Singh, Saransh; Das, Pinaki; Li, Yuelin; Schuman, Adam; Sinclair, Nicholas; Fezzaa, Kamel; Deriy, Alex; Leininger, Lara; Willey, Trevor M.

doi:10.1103/physrevb.102.104116

Cited by 17 publications

(13 citation statements)

References 46 publications

(51 reference statements)

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“…Dynamical hotspots can be significantly more reactive than thermodynamically equivalent ones created under non-shock conditions. 24,25 Path-dependent reactivity and mechanochemistry have been proposed to explain these observations. However, direct isolation of the underlying non-equilibrium mechanochemical processes and their effect on shock-induced chemistry remains elusive.…”

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confidence: 99%

“…These hotspots are almost exclusively characterized by their temperature fields. − However, recent molecular dynamics (MD) simulations indicate a deviation from this traditional picture. Dynamical hotspots can be significantly more reactive than thermodynamically equivalent ones created under nonshock conditions. , Path-dependent reactivity and mechanochemistry have been proposed to explain these observations. However, direct isolation of the underlying, nonequilibrium mechanochemical processes and their effect on shock-induced chemistry remains elusive.…”

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confidence: 99%

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Extemporaneous Mechanochemistry: Shock-Wave-Induced Ultrafast Chemical Reactions Due to Intramolecular Strain Energy

Hamilton

Kroonblawd

Strachan

2022

J. Phys. Chem. Lett.

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Regions of energy localization referred to as hotspots are known to govern shock initiation and the run-to-detonation in energetic materials. Mounting computational evidence points to accelerated chemistry in hotspots from large intramolecular strains induced via the interactions between the shockwave and microstructure. However, definite evidence mapping intramolecular strain to accelerated or altered chemical reactions has so far been elusive. From a large-scale reactive molecular dynamics simulation of the energetic material TATB, we map molecular temperature and intramolecular strain energy prior to reaction to decomposition kinetics. Both temperature and intramolecular strain are shown to accelerate chemical kinetics. A detailed analysis of the atomistic trajectory shows that intramolecular strain can induce a mechanochemical alteration of decomposition mechanisms. The results in this paper can inform continuum-level chemistry models to account for a wide range of mechanochemical effects. SM Figure 2: PE time history and reaction events time history. Total system PE (green) corresponds to the left y axis, both reaction events (red and blue) correspond to the right y axis.

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confidence: 99%

Extemporaneous Mechanochemistry: Shock-Wave-Induced Ultrafast Chemical Reactions Due to Intramolecular Strain Energy

Hamilton

Kroonblawd

Strachan

2022

J. Phys. Chem. Lett.

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“…It is not unreasonable to expect that the kinetic barrier between two dramatically different phases, like the ambient layered structure and a herringbone structure, is large, and thus pressure-induced amorphization and potential dissociation of the molecule is plausible at 7 GPa. To calculate this energy barrier, solid-state nudge elastic band calculations may be used, such as what was used to calculate the energy barrier for the graphite to diamond transformation. , Future experiments, such as pair distribution function and extended X-ray fine structure, can reveal whether the system is structurally amorphous and if the molecule is still intact.…”

Section: Discussionmentioning

confidence: 99%

High-Pressure Investigation of 2,4,6-Trinitro-3-bromoanisole (TNBA): Structural Determination and Piezochromism

et al. 2022

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Understanding phase transitions in energetic materials is crucial for developing predictive models of detonation. 2,4,6-Trinitro-3-bromoanisole (TNBA), an energetic material, was studied in its single-crystal form up to pressures of 45 GPa in a diamond anvil cell. The material was characterized by using X-ray, Raman, and optical transmission measurements. From single-crystal X-ray diffraction, the ambient structure of TNBA was determined which crystallizes in the P2 1 /c space group having four molecular units per unit cell. The X-ray data up to 9.2 GPa were fitted to a third-order Birch−Murnaghan equation of state by using the parameters K 0 = 13.2(2.4) GPa and K p = 5.1(1.4). Between 6.8 and 7.3 GPa, a phase transition was inferred in TNBA from concurrent fading of X-ray diffraction, disappearance of Raman peaks, increase in sample fluorescence, and discontinuous color change. The new phase was consistent with an amorphous state of at least partially intact molecules judging from the presence of higher-order Raman modes and irreversibility of the Raman spectra upon release. Piezochromism was observed with the translucent yellow TNBA gradually darkening and becoming opaque black at ∼25 GPa. This correlated to the absorption edge gradually shifting to the red in the visible spectrum. Signs of two possible additional structural transitions were detected in the 32.4−41.0 GPa range as suggested by a jump in the absorption edge, the irreversible changes in the absorption spectrum upon release to ambient pressure, and by the lack of Raman modes in recovered samples. The crystal and electronic structures of TNBA were also investigated up to 10 GPa by using DFT calculations and crystal structure prediction (CSP) simulations. In agreement with the experimentally observed transition at 7 GPa, the simulations at 10 GPa found a bevy of polymorphs lower in enthalpy and higher in density than P2 1 /c. The lowest calculated enthalpy structure was determined to be P2 1 2 1 2 1 , being in a different space group than the ambient experimental result.

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“…Various theoretical studies of the enthalpy in various phases indicated [39,40] that under compression above a few GPa, both CD and HD are more stable in comparison to HG, while CD is always more stable than HD. However, experimental measurements [8,11,[15][16][17][18] also show transformation from HG to HD.…”

Section: Introductionmentioning

confidence: 99%

Phase transition mechanism of hexagonal graphite to hexagonal and cubic diamond: ab initio simulation

Mittal

Chaplot

2021

J. Phys.: Condens. Matter

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Ab initio molecular dynamics simulations are used to elucidate the mechanism of the phase transition in shock experiments from hexagonal graphite (HG) to hexagonal diamond (HD) or to cubic diamond (CD). The transition from HG to HD is found to occur swiftly in very small time of 0.2 ps, with large cooperative displacements of all the atoms. We observe that alternate layers of atoms in HG slide in opposite directions by 1/6 along the ±[2, 1, 0], which is about 0.7 Å, while simultaneously puckering by about ±0.25 Å perpendicular to the a–b plane. The transition from HG to CD occurred with more complex cooperative displacements. In this case, six successive HG layers slide in pairs by 1/3 along [0, 1, 0], [−1, −1, 0] and [1, 0, 0], respectively along with the puckering as above. We have also performed calculations of the phonon spectrum in HG at high pressure, which reveal soft phonon modes that may facilitate the phase transition involving the sliding and puckering of the HG layers. We have further calculated the Gibbs free energy, including the vibrational energy and entropy, and derived the phase diagram between HG and CD phases.

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Detonation-induced transformation of graphite to hexagonal diamond

Cited by 17 publications

References 46 publications

Extemporaneous Mechanochemistry: Shock-Wave-Induced Ultrafast Chemical Reactions Due to Intramolecular Strain Energy

Extemporaneous Mechanochemistry: Shock-Wave-Induced Ultrafast Chemical Reactions Due to Intramolecular Strain Energy

High-Pressure Investigation of 2,4,6-Trinitro-3-bromoanisole (TNBA): Structural Determination and Piezochromism

Phase transition mechanism of hexagonal graphite to hexagonal and cubic diamond: ab initio simulation

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