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

Crystals

Santiago Sempere¹  Jordi Boronat¹  Anna Serra²  Claudio Cazorla³ 

[1] Departament de Física, Universitat Politècnica de Catalunya, Campus Nord B4-B5, E-08034 Barcelona, Spain;Departament d’Enginyeria Civil i Ambiental, Universitat Politècnica de Catalunya, Campus Nord C2, E-08034 Barcelona, Spain;School of Materials Science and Engineering, The University of New South Wales Australia, Sydney 2052, Australia;

关键词: dislocations;    rare-gas solids;    molecular dynamics;    quantum nuclear effects;   

DOI  :  10.3390/cryst8020064

来源: DOAJ

【 摘 要 】

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 hcp4He, 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.

【 授权许可】

Unknown