Probing the character of ultra-fast dislocations

Ruestes, Carlos J.; Bringa, Eduardo M.; Rudd, Robert E.; Remington, B. A.; Remington, Tané; Meyers, Marc A.

doi:10.1038/srep16892

Cited by 36 publications

(33 citation statements)

References 36 publications

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“…[11], we restrict our study of the phonon wind contribution to the drag coefficient to velocities comparable to but strictly less than c T , and dislocation-dislocation interactions are neglected. The case of supersonic dislocations is interesting in its own right, not least because of recent MD simulations in fcc metals that indicate the existence of dislocations moving at supersonic speeds; see [12][13][14][15][16] and references therein. Furthermore, supersonic dislocations have been observed experimentally in plasma crystals [17].…”

Section: Introduction and Outlinementioning

confidence: 99%

Dislocation drag from phonon wind in an isotropic crystal at large velocities

Blaschke

Mottola

Preston

2019

Philosophical Magazine

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The anharmonic interaction and scattering of phonons by a moving dislocation, the photon wind, imparts a drag force v B (v, T, ρ) on the dislocation. In early studies the drag coefficient B was computed and experimentally determined only for dislocation velocities v much less than transverse sound speed, c T . In this paper we derive analytic expressions for the velocity dependence of B up to c T in terms of the third-order continuum elastic constants of an isotropic crystal, in the continuum Debye approximation, valid for dislocation velocities approaching the sound speed. In so doing we point out that the most general form of the third order elastic potential for such a crystal and the dislocation-phonon interaction requires two additional elastic constants involving asymmetric local rotational strains, which have been neglected previously. We compute the velocity dependence of the transverse phonon wind contribution to B in the range 1%-90% c T for Al, Cu, Fe, and Nb in the isotropic Debye approximation. The drag coefficient for transverse phonons scattering from screw dislocations is finite as v → c T , whereas B is divergent for transverse phonons scattering from edge dislocations in the same limit. This divergence indicates the breakdown of the Debye approximation and sensitivity of the drag coefficient at very high velocities to the microscopic crystalline lattice cutoff. We compare our results to experimental results wherever possible and identify ways to validate and further improve the theory of dislocation drag at high velocities with realistic phonon dispersion relations, inclusion of lattice cutoff effects, MD simulation data, and more accurate experimental measurements. arXiv:1907.00101v2 [cond-mat.mtrl-sci] 1 Oct 2019

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Section: Introduction and Outlinementioning

confidence: 99%

Dislocation drag from phonon wind in an isotropic crystal at large velocities

Blaschke

Mottola

Preston

2019

Philosophical Magazine

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“…In real-world solids, there is some evidence that edge dislocations can move "transonically" with speeds up to the longitudinal velocity c L , see, e.g., Ref. [74]. A difficulty is that the arguments for emergent Lorentz invariance become precise near the continuous quantum phase transition, while deep in the solid "irrelevant" operators such as the nature of the chemical bond may become important; e.g., dislocations in covalent solids are immobile, while simple metals are malleable because of the rather isotropic nature of their electronic binding forces.…”

Section: A Dislocation Worldsheetsmentioning

confidence: 99%

Dual gauge field theory of quantum liquid crystals in three dimensions

Beekman

Nissinen

et al. 2017

Phys. Rev. B

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The dislocation-mediated quantum melting of solids into quantum liquid crystals is extended from two to three spatial dimensions, using a generalization of boson-vortex or Abelian-Higgs duality. Dislocations are now Burgers-vector-valued strings that trace out worldsheets in space-time while the phonons of the solid dualize into two-form (Kalb-Ramond) gauge fields. We propose an effective dual Higgs potential that allows for restoring translational symmetry in either one, two, or three directions, leading to the quantum analogues of columnar, smectic, or nematic liquid crystals. In these phases, transverse phonons turn into gapped, propagating modes, while compressional stress remains massless. Rotational Goldstone modes emerge whenever translational symmetry is restored. We also consider the effective electromagnetic response of electrically charged quantum liquid crystals, and find among other things that as a hard principle only two out of the possible three rotational Goldstone modes are observable using propagating electromagnetic fields.

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“…Moreover, very limited, if any, phase transformation is induced far from the shock front, i.e., plasticity is almost solely dislocation-mediated. In Figure 3a we show compressive stress profiles along the shock direction ( ) at t=4, 9, and 14 Accepted in Computational Materials Science [10] ps, after initial contact of the piston with the sample. The average particle velocities and virial stress tensor are calculated for slabs of atoms of thickness of 0.7 nm in the z direction.…”

Section: Molecular Dynamics Simulation Resultsmentioning

confidence: 99%

“…Even in plane and car crashes, high pressures and high strain rates with large plastic deformation can occur [4]. Despite the considerable amount of research, only recently experiments [5][6][7][8] and numerical simulations [9][10][11] were able to shed some light on the microstructural origins of plastic deformation in metals during the initial stage of shock compression.…”

Section: Introductionmentioning

confidence: 99%

Shear relaxation behind the shock front in 110 molybdenum – From the atomic scale to continuous dislocation fields

Kositski

Steinberger

Sandfeld

et al. 2018

Computational Materials Science

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In this work we study shock-induced plasticity in Mo single crystals, impacted along the <110> crystal orientation. In particular, the shear relaxation behind the shock front is quantitatively inspected. Molecular dynamics (MD) simulations are employed to simulate the deformation during shock, followed by post-processing to identify and quantify the dislocation lines nucleated behind the shock front. The information on the dislocation lines is ensemble averaged inside slabs of the simulation box and over different realizations of the MD simulations, from which continuous dislocation fields are extracted using the Discrete-to-Continuous method. The continuous dislocation fields are correlated with the stress and strain fields obtained from the MD simulations. Based on this analysis, we show that the elastic precursor overshoots the shear stress, after which dislocations on a specific group of slip planes are nucleated, slightly lagging behind the elastic front. Consequently, the resolved shear stress is relaxed, but the principal lateral stress increases. The latter leads to an increase in the resolved shear stress on a plane parallel to the shock wave, resulting in an additional retarded front of dislocation nucleation on planes parallel to the shock front. Finally, the twostage process of plasticity results in an isotropic stress state in the plane parallel to the shock wave. The MD simulation results are employed to calculate the dislocation densities on specific slip planes and the plastic deformation behind the shock, bridging the gap between the information on the atomic scale and the continuum level.

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Probing the character of ultra-fast dislocations

Cited by 36 publications

References 36 publications

Dislocation drag from phonon wind in an isotropic crystal at large velocities

Dislocation drag from phonon wind in an isotropic crystal at large velocities

Dual gauge field theory of quantum liquid crystals in three dimensions

Shear relaxation behind the shock front in 110 molybdenum – From the atomic scale to continuous dislocation fields

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