Structural Rearrangement of Energetic Materials under an External Electric Field: A Case Study of Nitromethane

Abstract

As a significant stimulus, the external electric field (EEF) can change the decomposition mechanism and energy release of energetic materials (EMs). Hence, understanding the response of EMs to an EEF is greatly meaningful for their safe usage. Herein, the structural arrangement, a crucial factor in the impact sensitivity and detonation performance of EMs, under the EEF ranging from 0.0 to 0.5 V/Å was investigated via molecular dynamics simulation. Nitromethane (NM) was taken as a case study due to the simple structure. The simulation results show that there exists a critical EEF strength between 0.2 and 0.3 V/Å, which can induce the transition of NM molecules from relatively disordered distribution to solidlike ordered and compacted arrangement with a large density. In this ordered structure, NM dipoles are aligned in a head-to-tail pattern parallel to the EEF direction because of the favored dipole-dipole interactions and weak C-H···O hydrogen bonds. As the EEF strength is enhanced, the potential energy and cohesive energy density of the NM system gradually decrease and increase, respectively, indicative of high thermodynamics stability of ordered arrangement. The results reported here also shed light on the potential of the EEF to induce the nucleation and crystallization to explore new polymorphs of EMs.

Melting Point Prediction of Energetic Materials via Continuous Heating Simulation on Solid-to-Liquid Phase Transition

“…After geometry optimization with the COMPASS force field, these lattice parameters became a = 4.864 Å, b = 6.187 Å, and c = 8.384 Å, suggestive of an acceptable accuracy, that is, a relative deviation within 7%, for MD simulation of solid phase. Additionally, previous simulation shows that the experimental density of liquid NM can be greatly reproduced by the COMPASS force field . Hence, the COMPASS force field, an ab initio force field, was utilized to describe the solid-to-liquid phase transition.…”

“…Additionally, previous simulation shows that the experimental density of liquid NM can be greatly reproduced by the COMPASS force field. 29 Hence, the COMPASS force field, an ab initio force field, was utilized to describe the solid-to-liquid phase transition. Coulomb's law and Lennard−Jones (9-6) potential are employed to describe the nonbonding interactions in COMPASS.…”

External Electric Field-Induced Phase Transition of a Series of Energetic Pentazole Crystals: A First-Principles Study

“…As an important external stimulus, the external electric field could change the physicochemical properties for energetic materials by changing the structures of molecules or ions, such as molecular rearrangements and conformational changes. , Politzer et al − reported the effect of external electric field on the trigger bonds in energetic materials, such as C–NO 2 , N–N 2 , O–NO 2 , and N–NO 2 . The results suggested that the strength of these trigger bonds can be improved along the external electric field direction owing to the enhancement of intrinsic molecular polarities.…”

Structural and physical properties of trichloroethylene under an external electric field

“…Under the action of EEF, many new chemical changes and phenomena, such as chemical bond breaking, decomposition mechanism, new free radical generation, and vibration Stark effect, emerge. [ 13–18 ] These variations are imperative to understand the characteristics of molecules.…”