The molecular geometries of some cyclic nitramines in the gas phase

Shishkov, Igor F.; Vilkov, L. V.; Kolonits, Mária; Rozsondai, B.

doi:10.1007/bf00673490

Cited by 51 publications

(71 citation statements)

References 13 publications

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“…In both the long and short cells, around 30% of the molecules in the shear bands are not in the AAE conformation once a steady-fluctuating state is achieved. Although the AAA conformation is suggested to be favored in the gas phase, 42,43 we detect only a negligible number of molecules in this conformation in the condensed phase.…”

Section: Molecular Conformationmentioning

confidence: 55%

Shock-induced shear bands in an energetic molecular crystal: Application of shock-front absorbing boundary conditions to molecular dynamics simulations

et al. 2008

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W91INF-05-1-0265 REPORT NUMBER REPORT ~'u~mER 48101-EG-MUR The views, opinions andlor findings contained in this report are those of the author(s) and should not be construed as an official Department of the Army position, policy or decision, unless so designated by other documentation. Approved for public release; federal purpose rights The response of the energetic molecular crystal cyclotrimethylene trinitramine (RDX) to the propagation of planar shock waves nonnal to (100) has been studied using large-scale molecular dynamics simulations that employ an accurate and transferable nonreactive potential. The propagation of the shock waves was simulated using nonequilibrium molecular dynamics. Shear bands were nucleated during shocks with a particle velocity of 1.0 km s-I and corresponding Rankine-Hugoniot shock pressun of9.7 GPa. These defects propagate into the compressed material at 45° to (100) in the (010) zone. The shear bands e\'oh'e slowly compared to the time scales routinely accessible to nonequilibrium molecular dynamics toward a liquidlike state as a result of viscous heating. A recently developed shock-front absorbing boundary condition [AV. Bolesta et al. , Phys. Rev. B 76, 224108 (2007)] was applied to the simulation cells at the moment of maximum compression to sustain the shock-compressed state. Molecular dynamics simulations were then employed to study the temIXlral and structural evolution of the shock-induced shear bands toward a steady-fluctuating state. Owing to the intense, viscous flow-driven heati ng within the shear bands. these defects can be considered to be homogeneously nucleated hot spots.

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Section: Molecular Conformationmentioning

confidence: 55%

Shock-induced shear bands in an energetic molecular crystal: Application of shock-front absorbing boundary conditions to molecular dynamics simulations

et al. 2008

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“…As was already pointed out, however, the energetic consequences of the conceptual differences between E int , E * int , and ⌬E stab are often rather small. It might be anticipated that this potential problem would be exacerbated in the case of RDX because the molecular conformation changes from chair-AAA in the gas phase [28,29] to chair-AAE in the crystal [11]. However the MP2/6-31G* and B3LYP/6-311ϩG** analyses of Rice and Chabalowski [29] show the AAA and AAE conformers to differ in energy by only 0.13 and 0.64 kcal/mol, respectively.…”

Section: Figure 3 Two Molecules In Neighboring Interlockedmentioning

confidence: 93%

“…(2) and (3), is normally calculated using the ground-state gasphase geometries of the interacting molecules. In the case of RDX, this would mean the chair-AAA molecular conformation [28,29]. Because our interest is in interactions within the crystal, however, it is more relevant to use the chair-AAE, which is the conformation of the RDX molecule in the lattice [11].…”

Section: Methodsmentioning

confidence: 99%

Noncovalent intermolecular energetics: RDX crystal

Politzer

2004

Int J of Quantum Chemistry

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ABSTRACT:A methodology for using electronic densities to determine electrostatic, polarization, and total energies of noncovalent interactions is summarized and applied to two key molecular pair combinations in the crystal lattice of RDX (hexahydro-1,3,5-trinitro-s-triazine). It is found that the total interaction energies can be well approximated as purely electrostatic between RDX molecules in the chair-AAE conformation. However, Mulliken and CHelpG point-charge models are not adequate for reproducing these energies.

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“…All calculations started with RDX in a chair conformation with all NO 2 groups in the axial position (RDX‐AAA), claimed to be the global minimum by previous theoretical and experimental studies. A more recent study by Molt et al found that the AAA conformation is 1.2 kcal/mol higher in energy than RDX, where two NO 2 groups are in axial position and one group is in equatorial position (AAE) .…”

Section: Computational Detailsmentioning

confidence: 99%

The effect of external forces on the initial dissociation of RDX (1,3,5-trinitro-1,3,5-triazine): A mechanochemical study

2017

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Experimental and theoretical studies have proposed different initiation reactions for the decomposition of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). Three primary reactions are considered to start RDX decomposition: homolytic NAN bond fission, HONO elimination, and concerted fission of CAN bonds. The focus of this article is to study the effect of external forces on the energy barrier and reaction energies of all three mechanisms. We used the Nudged Elastic Band method along with ab initio Density Functional Theory within the framework of a generalized force-modified potential energy surface (G-FMPES) to calculate the minimum energy paths at different compressive (corresponding to pressure between approximately 6 and 294 MPa) andexpansive force values (between 10 and 264 pN). For all three reactions, the application of an expansive force increases the exothermicity and lowers the energy barriers to different extents, while a compressive force decreases the exothermicity and raises the energy barrier to different extents. K E Y W O R D SDFT, G-FMPES, mechanochemistry, RDX, shock wave | I N T R O D U C T I O NHexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is an important chemical compound widely used as a propellant and an explosive. It is also the smallest compound with qualities very similar to more powerful explosives like HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazocine) and CL20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane). RDX has been investigated for over 60 years on the nature of its structure [1][2][3][4][5][6][7] and on the nature of its decomposition mechanism by both experimental [8][9][10][11][12][13][14][15][16][17][18][19][20][21] and theoretical [3,[22][23][24][25][26][27][28][29] studies. Structural studies have shown that several conformers of RDX can coexist [7,30,31] and due to the low energy barrier, the various RDX forms can easily interconvert into one another. With regard to the decomposition mechanism of RDX, different possibilities have been investigated as initial dissociation reactions (see Figure 1). The lowest activation energies have been found for the homolytic NAN fission and the HONO elimination [23][24][25]29,32] ; rendering the concerted fission of CAN bonds (previously thought to be the primary decomposition path [13] ) as a secondary initiation path. However, experimental studies have shown evidence for all three mechanisms. The concerted mechanism was observed only in gas phase experiments, [13,33] while the other two mechanisms, NAN fission and HONO elimination, were observed in crystalline RDX. [20,34] For example, Patterson et al. [20] used time-resolved spectroscopy to study the decomposition of RDX induced by shock wave, and they found evidence that supports the NAN fission and the HONO elimination mechanisms.Theoretical studies that calculate energy barriers [25] for the decomposition mechanisms have focused on calculations in the gas phase. However, most scenarios that lead to RDX decomposition involve the passage of a shock wave or other exte...

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The molecular geometries of some cyclic nitramines in the gas phase

Cited by 51 publications

References 13 publications

Shock-induced shear bands in an energetic molecular crystal: Application of shock-front absorbing boundary conditions to molecular dynamics simulations

Shock-induced shear bands in an energetic molecular crystal: Application of shock-front absorbing boundary conditions to molecular dynamics simulations

Noncovalent intermolecular energetics: RDX crystal

The effect of external forces on the initial dissociation of RDX (1,3,5-trinitro-1,3,5-triazine): A mechanochemical study

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