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Crystals 2018, 8(2), 64; https://doi.org/10.3390/cryst8020064

Dislocation Structure and Mobility in Hcp Rare-Gas Solids: Quantum versus Classical

1
Departament de Física, Universitat Politècnica de Catalunya, Campus Nord B4-B5, E-08034 Barcelona, Spain
2
Departament d’Enginyeria Civil i Ambiental, Universitat Politècnica de Catalunya, Campus Nord C2, E-08034 Barcelona, Spain
3
School of Materials Science and Engineering, The University of New South Wales Australia, Sydney 2052, Australia
*
Author to whom correspondence should be addressed.
Received: 13 December 2017 / Revised: 17 January 2018 / Accepted: 20 January 2018 / Published: 29 January 2018
(This article belongs to the Special Issue Quantum Crystals)
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Abstract

We study the structural and mobility properties of edge dislocations in rare-gas crystals with the hexagonal close-packed (hcp) structure by using classical simulation techniques. Our results are discussed in the light of recent experimental and theoretical studies on hcp 4 He, an archetypal quantum crystal. According to our simulations classical hcp rare-gas crystals present a strong tendency towards dislocation dissociation into Shockley partials in the basal plane, similarly to what is observed in solid helium. This is due to the presence of a low-energy metastable stacking fault, of the order of 0.1 mJ/m 2 , that can get further reduced by quantum nuclear effects. We compute the minimum shear stress that induces glide of dislocations within the hcp basal plane at zero temperature, namely, the Peierls stress, and find a characteristic value of the order of 1 MPa. This threshold value is similar to the Peierls stress reported for metallic hcp solids (Zr and Cd) but orders of magnitude larger than the one estimated for solid helium. We find, however, that in contrast to classical hcp metals but in analogy to solid helium, glide of edge dislocations can be thermally activated at very low temperatures, T∼10 K, in the absence of any applied shear stress. View Full-Text
Keywords: dislocations; rare-gas solids; molecular dynamics; quantum nuclear effects dislocations; rare-gas solids; molecular dynamics; quantum nuclear effects
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Sempere, S.; Serra, A.; Boronat, J.; Cazorla, C. Dislocation Structure and Mobility in Hcp Rare-Gas Solids: Quantum versus Classical. Crystals 2018, 8, 64.

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