Mechanochemistry: The Effect of Dynamics

Smalø, Hans S.; Rybkin, Vladimir V.; Klopper, Wim; Helgaker, Trygve; Uggerud, Einar

doi:10.1021/jp504959z

Cited by 27 publications

(33 citation statements)

References 40 publications

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“…Here, the application of mechanical forces on a system alters the potential energy surface (PES), and consequently, reaction pathways and rates. The effects of external forces were recently investigated for several different systems . Moreover, recent reviews were also published on the topic of mechanochemistry .…”

Section: Introductionmentioning

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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Section: Introductionmentioning

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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“…Uggerud and coworkers used EFEI-based MD simulations in conjunction with DFT calculations and models consisting of a chain of Morse potentials to study the basic features of mechanochemical processes under dynamic conditions [104]. The results of this study showed that the simple model consisting of Morse potentials is adequate for describing the F-dependent dynamics of polymers, which may reduce the computational costs of simulations of mechanochemical processes.…”

Section: Application Of F Between Atomsmentioning

confidence: 94%

Theoretical Approaches for Understanding the Interplay Between Stress and Chemical Reactivity

Kochhar

Heverly‐Coulson

Mosey

2015

Topics in Current Chemistry

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The use of mechanical stresses to induce chemical reactions has attracted significant interest in recent years. Computational modeling can play a significant role in developing a comprehensive understanding of the interplay between stresses and chemical reactivity. In this review, we discuss techniques for simulating chemical reactions occurring under mechanochemical conditions. The methods described are broadly divided into techniques that are appropriate for studying molecular mechanochemistry and those suited to modeling bulk mechanochemistry. In both cases, several different approaches are described and compared. Methods for examining molecular mechanochemistry are based on exploring the force-modified potential energy surface on which a molecule subjected to an external force moves. Meanwhile, it is suggested that condensed phase simulation methods typically used to study tribochemical reactions, i.e., those occurring in sliding contacts, can be adapted to study bulk mechanochemistry.

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“…Of course, which of the two equal y ‐bonds breaks first depends on the thermal noise in reality and may also depend on nonequilibrium effects which may be described by a Franck–Condon theory of mechanochemistry . The effects of thermal fluctuations have already been demonstrated to play a key role in mechanochemistry . As a real chemical example we have the flattening of the OSiO bond angles in siloxanes, see for example, Refs.…”

Section: Case Of a Planar 4‐atomic Abba Molecule With C 2h Symmetrymentioning

confidence: 99%

“…[13] An algorithm to locate optimal BBPs has been recently proposed. [66] Note that a bond will actually break before the BBP due to finite temperature effects [67][68][69] or by the zero point energy of the corresponding bond. The kinetics of the break caused mainly by the force can be explained by a usual escape of the molecular state over the decreasing barrier.…”

Section: Application Of Newton Trajectoriesmentioning

confidence: 99%

“…[106] The effects of thermal fluctuations have already been demonstrated to play a key role in mechanochemistry. [68] As a real chemical example we have the flattening of the O Si O bond angles in siloxanes, see for example, Refs. [107,108] 7 | CASE OF A PLANAR 4-RING AABB MOLECULAR MODEL WITH DIAGONAL PULLING…”

Section: Case Of a Planar 4-atomic Abba Molecule With C 2 H Symmetrymentioning

confidence: 99%

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Toward a theory of mechanochemistry: Simple models from the very beginnings

Quapp

Bofill

Ribas‐Ariño

2018

Int J of Quantum Chemistry

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A core idea in the context of mechanochemistry is that applying an external tensile force along a reaction coordinate should enhance the chemical reaction of interest. Here, we analyze perturbed generic molecular structures: schematic models of triatomics, ABC, and tetraatomics, AABB. They are used to demonstrate that pulling does usually not use the “reaction coordinate,” but opens new reaction pathways. Within development of these models we use the concept of Newton trajectories for a theory of mechanochemistry. However, we find cases where the theory of Newton trajectories is not applicable. For all cases, we define the curve of force‐displaced stationary points, and we discuss the importance of barrier breakdown points and valley‐ridge inflection points. The examples use Morse potentials for bonds and simple angle functions and are demonstrated by assumed real values for the potential parameters. On the basis of the systematic study of some generic models we explain a set of already observed experimental mechanochemical phenomena in specific molecular systems and we apply the results to the strength of chemical bonds.

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Mechanochemistry: The Effect of Dynamics

Cited by 27 publications

References 40 publications

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

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

Theoretical Approaches for Understanding the Interplay Between Stress and Chemical Reactivity

Toward a theory of mechanochemistry: Simple models from the very beginnings

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