Observation of helicoidal dislocation lines in fluorite crystals

Bontinck, W.; Amelinckx, S.

doi:10.1080/14786435708231726

Cited by 78 publications

(5 citation statements)

References 4 publications

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“…The formation of a single helix as a result of vacancy absorption has been studied ever since the first report by Bontinck and Amelinckx. , More recently, the formation of single helix dislocations was reported by Haley et al in Fe-9Cr alloys, where screw dislocations acquired helical character by absorption of vacancies produced by neutron irradiation. Since the neutron damage produced vacancy and interstitial (Frenkel) pairs, the absorption of vacancies by screw dislocations enhanced the clustering of interstitials in the form of loops in the vicinity of helical dislocations.…”

Section: Resultsmentioning

confidence: 99%

Discovery of Double Helix and Impact on Nanoscale to Mesoscale Crystalline Structures

Narayan

2022

ACS Omega

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Screw dislocations play a significant role in the growth of crystalline structures by providing a continuous source of surface steps which represent available sites for crystal growth. Here, we show that pure screw dislocations can become helical from the absorption of defects (e.g., vacancies) and develop an attractive interaction with another helical dislocation to form a double helix of screw dislocations. These single and double helices of screw dislocations can result in the formation of interesting nanostructures with large Eshelby twists. We have previously proposed the formation of a double helix of screw dislocations to explain large Eshelby twists in crystalline nanostructures ( Mater. Res. Lett. 2021 9 453 457 ). We now show direct evidence for the formation of a double helix during thermal annealing of screw dislocations. The large Burgers vectors associated with these dislocations are used to explain the presence of large Eshelby twists in PbSe and PbS (NaCl cubic structure) and InP and GeS (wurtzite hexagonal structure) nanowires. These single- and double-helix screw dislocations can also combine to create even larger super Burgers vectors. These large effective Burgers also unravel the mechanism for the formation of nanopipes and micropipes with hollow cores and nanotubes with Eshelby twists in technologically important materials such as SiC, GaN, and ZnO that are utilized in a variety of advanced solid-state devices.

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Section: Resultsmentioning

confidence: 99%

Discovery of Double Helix and Impact on Nanoscale to Mesoscale Crystalline Structures

Narayan

2022

ACS Omega

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“…It is well known that dislocations play the role of sinks and sources of point defects. The formation of helical dislocations after irradiation has been observed for a long time [16] and discussed theoretically [17][18][19] and numerically [20][21][22]. However, although the advanced (equilibrium), helical, form of dislocation in the presence of supersaturation or undersaturation of point defects is well established [17], the mechanisms of nucleation are rather poorly documented from an observational point of view.…”

Section: Experimental Study Of Dislocation Evolutionmentioning

confidence: 99%

4D electron tomography of dislocations undergoing electron irradiation

Mussi¹,

Carrez²,

Gouriet³

et al. 2021

Comptes Rendus. Physique

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Imaging dislocation microstructures in 3D and monitoring their interactions over time is a major challenge. In this study, we show that enhancing the contrast of dislocation lines prior to reconstruction, allows to optimize an acquisition phase with fewer images and thus to follow the 3D evolution of a microstructure over time. We illustrate this new possibility by studying the first stages of formation of helical dislocations in MgO under electron irradiation. We highlight the role of segment mobility on the initiation of climb and reveal the existence of preferential mixed climb planes.

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“…To verify the general applicability of the method introduced above, it is applied to generate a dislocation helix with complex geometry. Dislocation helices are widely observed in metallic, ionic and covalent crystals [25][26][27][28], where an excess of point defects exists. A dislocation helix can be produced by the climb bow-out of a dislocation line with a screw or mixed character, accompanying the vacancy emission or absorption from the original dislocation line [20].…”

Section: Dislocation Helixmentioning

confidence: 99%

“…For example, dislocation lines may curve in the three dimensions, e.g. dislocation helices [25][26][27][28] observed in materials with an excess of point defects. A dislocation loop can have the Burgers vector components both in the loop plane and normal to the loop plane, e.g.…”

Section: Introductionmentioning

confidence: 99%

A general method to construct dislocations in atomistic simulations

Zhang

2019

Modelling Simul. Mater. Sci. Eng.

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An important aspect of atomistic simulations of dislocations is the construction of the initial dislocation configurations. However, limited configurations can be constructed by previous methods, impeding the simulations of a general dislocation configuration in real materials. In this paper, we develop a simple and general method for constructing dislocations with arbitrary shapes specified by the users, realising the Volterra process at the atomic level. Examples of its applications to a dislocation helix, the partial dislocations, the multidislocation configurations, and the dislocations in the imperfect crystal are presented, showing the capacity and robustness of the present method.

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Observation of helicoidal dislocation lines in fluorite crystals

Cited by 78 publications

References 4 publications

Discovery of Double Helix and Impact on Nanoscale to Mesoscale Crystalline Structures

Discovery of Double Helix and Impact on Nanoscale to Mesoscale Crystalline Structures

4D electron tomography of dislocations undergoing electron irradiation

A general method to construct dislocations in atomistic simulations

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