Elastic Coefficients of β-HMX as Functions of Pressure and Temperature from Molecular Dynamics

Pereverzev, Andrey; Sewell, Tommy

doi:10.3390/cryst10121123

Cited by 27 publications

(46 citation statements)

References 33 publications

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“…As discussed above, this is not unique to nanoindentation as other means of experimental determination of elastic moduli for this material also present discrepancies. It should be noted however, that values obtained present a similarity to values obtained by molecular dynamics simulations [31] with a maximum of 12% error, and otherwise reasonably fit into the statistically determined range of values presented, obtained from both numerical and experimental methods. Moreover, the values obtained in this work agree with most works which show E 22 to be the largest and E 33 to be the smallest moduli.…”

Section: Resultssupporting

confidence: 77%

Experimental study of anisotropic constitutive behavior of β-HMX crystals via nanoindentation and small-scale dynamic impact

et al. 2021

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For energetic crystals such as HMX, the sensitivity of the material to shock, the possibility of initiation, and the subsequent reaction is known to be controlled by processes occurring at the crystal level. The anisotropic nature of β-HMX can be critical in determining the performance of HMX based polymer bonded explosives, which are widely used across multiple industries as propellant or explosives. In this work, we experimentally obtain constitutive parameters for characterizing the response of multiple crystalline planes of β-HMX crystals to external loading. Nanoindentation and small-scale dynamic impact experiments were performed on multiple planes of β-HMX crystals to comparatively measure the indentation moduli in multiple orientation directions. Anisotropic material behavior, involving constitutive elastic and non-elastic parameters, was measured and studied. Findings regarding material properties for the (100), (010), (001), {110}, and {011} planes of β-HMX are presented and compared with literature data.

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Section: Resultssupporting

confidence: 77%

Experimental study of anisotropic constitutive behavior of β-HMX crystals via nanoindentation and small-scale dynamic impact

et al. 2021

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“…The effective moduli

G

corresponding to the selected planes and directions are listed in Table 2. These are obtained based on the pressure‐dependent elastic stiffness tensor of β‐HMX reported in [24] for the temperature of the present simulations, 300 K. The values of

q

vary from system to system and are smaller than that predicted with Eq. (1).…”

Section: Resultsmentioning

confidence: 68%

“…Molecular crystals have much larger lattice parameters and larger interplanar distances compared to monatomic crystals. This geometric detail, in conjunction with the relatively weak intermolecular bonding, render molecular crystals elastically softer than monatomic crystals [13,23,24]. Compressive hydrostatic stresses lead to molecular interlocking, which implies large pressure sensitivity of the flow stress [10] -a phenomenon usually neglected in high symmetry monatomic crystals.…”

Section: Introductionmentioning

confidence: 99%

Homogeneous Dislocation Nucleation in Molecular Crystal Cyclotetramethylene‐Tetranitramine (β‐HMX)

Zhang

Picu

2022

Propellants Explo Pyrotec

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The molecular crystal cyclotetramethylene‐tetranitramine (β‐HMX) is the active ingredient in some broadly used plastic bonded explosives. Plasticity is thought to be essential for reaction initiation and detonation. In this work we use molecular simulations to investigate the conditions under which dislocations nucleate homogeneously in β‐HMX. We evaluate the resolved shear stress leading to homogeneous nucleation of dislocation loops in the planes currently considered to be most important for plasticity in this crystal, (011) and (101), and at pressures up to 20 GPa. The importance of homogeneous nucleation for plastic deformation is discussed in relation to the other plasticity mechanisms operating in HMX. It is concluded that homogeneous nucleation is unlikely to happen at pressures above 5 GPa, while at pressures below this threshold homogeneous nucleation competes with shear localization. The article also presents γ‐surfaces for the (011) and (101) planes, which are used here to interpret the nucleation process and critical stresses, and have broader importance in other contexts. A discussion of the procedure required to compute γ‐surfaces in molecular crystals is included.

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“…Then, the RDX crystal can be optimized in a targeted manner. The molecular dynamics simulation was used to simulate many properties before, such as mechanical properties, prediction of crystal morphology, and so on, and the results are all in good agreement with experiments [13][14][15][16][17][18]. The simulation method provides a safe, convenient, fast, and low-cost way to study the influence of internal defects on the sensitivity of RDX crystals.…”

Section: Introductionmentioning

confidence: 67%

Molecular Dynamics Simulation of the Influence of RDX Internal Defects on Sensitivity

et al. 2021

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The internal defect is an important factor that could influence the energy and safety properties of energetic materials. RDX samples of two qualities were characterized and simulated to reveal the influence of different defects on sensitivity. The internal defects were characterized with optical microscopy, Raman spectroscopy and microfocus X-ray computed tomography technology. The results show that high-density RDX has fewer defects and a more uniform distribution. Based on the characterization results, defect models with different defect rates and distribution were established. The simulation results show that the models with fewer internal defects lead to shorter N-NO2 maximum bond lengths and greater cohesive energy density (CED). The maximum bond length and CED can be used as the criterion for the relative sensitivity of RDX, and therefore defect models doped with different solvents are established. The results show that the models doped with propylene carbonate and acetone lead to higher sensitivity. This may help to select the solvent to prepare low-sensitivity RDX. The results reported in this paper are aiming at the development of a more convenient and low-cost method for studying the influence of internal defects on the sensitivity of energetic materials.

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Elastic Coefficients of β-HMX as Functions of Pressure and Temperature from Molecular Dynamics

Cited by 27 publications

References 33 publications

Experimental study of anisotropic constitutive behavior of β-HMX crystals via nanoindentation and small-scale dynamic impact

Experimental study of anisotropic constitutive behavior of β-HMX crystals via nanoindentation and small-scale dynamic impact

Homogeneous Dislocation Nucleation in Molecular Crystal Cyclotetramethylene‐Tetranitramine (β‐HMX)

Molecular Dynamics Simulation of the Influence of RDX Internal Defects on Sensitivity

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