Molecular Dynamics Studies of the Structural Change in 1,3-Diamino-2,4,6-trinitrobenzene (DATB) in the Crystalline State under High Pressure

Abstract

Molecular dynamics (MD) calculations were performed to reveal the effect of high pressure on the crystal of 1,3-diamino-2,4,6-trinitrobenzene (DATB). The coordinates of the individual atoms in the DATB crystal structure were obtained using X-ray diffraction analysis. The primary simulation cell consists of 54 molecules in a monoclinic cell, corresponding to 27 unit cells obtained by replicating the experimentally determined unit cell. The pressure dependence of intermolecular distance concerning hydrogen bonds in the DATB crystal was investigated in the range of 1 atm to 25.0 GPa by increasing the pressure at every 0.5 GPa. Intermolecular distances of the hydrogen bonds between the nitro and amino groups decrease with increasing pressure up to 25.0 GPa, except in the range of 7.5 to 8.5 GPa. A unique structural change in the DATB crystal occurred at approximately 7.5 GPa. Intermolecular distances began to remarkably increase at 7.5 GPa and kept increasing until 8.5 GPa. To clarify the origin of this strange behavior, we used the same pressure regions as those above to analyze the changes in the dihedral angles defined by the plane of the nitro or amino group and by the aromatic rings of hydrogen bonds. The results showed a strong correlation between the increment of the intermolecular distances and the changes in the dihedral angles for these groups. Moreover, when the pressure dependence of the crystal parameter was analyzed, it was found that the a-axis length did not change despite the change in the lengths of the other two axes. The direction of the a axis corresponds to the direction of intermolecular hydrogen bond networks in the crystal. The results of the present MD calculations explained our previous results for Raman spectra measurements. Further analysis showed that these hydrogen bonds play an important role in stabilizing the energy change of the crystal system.

Trigger bond analysis of nitroaromatic energetic materials using wiberg bond indices

“…Further increasing the number of hydrogen bonding interactions to a nitro group from one to two further enhances the double‐bond character. In DATB, the trigger bond is the nitro with one hydrogen bond ( d CNO 2 = 1.458 Å (%ΔWBI = +6.54%)) given that the nitro group with two hydrogen bonding interactions is stabilized by enhanced partial double bond character ( d CNO 2 = 1.444 Å (%ΔWBI = +12.53%)) which agrees with previous results . In addition, HNDPA and TETNPO have intramolecular hydrogen bonding with an NH group which stabilized those CNO 2 trigger bonds.…”

“…The DFT(M06‐2X)/TZVP optimized structures are in good agreement with available X‐ray crystallographic data and previous DFT calculations for 35 of the 63 nitroaromatic energetic molecules. The optimized structures of the 63 nitroaromatic energetic molecules are included in the Supporting Information (Figs.…”

“…S1–S7). Generally, the DFT‐optimized CNO 2 bond distances are slightly longer than experimental values (Table ) and intramolecular NH···ONO and OH···ONO interactions are shorter than those found in experiment . Intramolecular interactions between the nitro and amino or hydroxyl groups force near‐planar ring conformations for the aniline‐ and phenol‐based energetic materials.…”

The Behavior of Ionic Liquids under High Pressure: A Molecular Dynamics Simulation

“…Using MD simulations, the CHARMM, 26 AMBER, 27,28 OPLS, 29,30 and GROMOS 31 34 used this method to study the phase diagram of water at high pressures where spontaneous freezing of the liquid into a solid phase at pressures of about 80 000 bar was observed. Kohno et al 35 reported the effect of high pressure on the crystal structure of 1,3-diamino-2,4,6-trinitrobenzene and a unique structural change was found around 75 000 bar by molecular simulation. Meher et al 36 have studied the effect of pressure on the conformation and dynamics of HIV-1 protease at 1 and 3000 bar pressure conditions using an AMBER force field.…”

Theoretical studies on the thermodynamic properties and detonation properties of cyclotrimethylene trinitramine (RDX) with aluminum and boron metals.

“…(RDX) (C3N6O6H6) is a significant energetic material which is used as propellants and explosives. In the literature, there are numerous studies on RDX explosives focusing on their detonation performance and thermal stability [9][10][11][12]. Since there are limited studies on the explosives with composite RDX-Al and RDX-B derivatives including their thermodynamic properties, this study is expected to contribute to fill this gap in the literature.…”