Dislocations and vacancies in two-dimensional mixed crystals of spheres and dimers

Gerbode, Sharon J.; Ong, Desmond C.; Liddell, Chekesha M.; Cohen, Itai

Dislocations and vacancies in two-dimensional mixed crystals of spheres and dimers

Type

Article

Authors

Gerbode, Sharon J.
Ong, Desmond C.
Liddell, Chekesha M.
Cohen, Itai

KAUST Grant Number

KUS-C1-018-02

Date

2010-10-15

Abstract

In colloidal crystals of spheres, dislocation motion is unrestricted. On the other hand, recent studies of relaxation in crystals of colloidal dimer particles have demonstrated that the dislocation dynamics in such crystals are reminiscent of glassy systems. The observed glassy dynamics arise as a result of dislocation cages formed by certain dimer orientations. In the current study, we use experiments and simulations to investigate the transition that arises when a pure sphere crystal is doped with an increasing concentration of dimers. Specifically, we focus on both dislocation caging and vacancy motion. Interestingly, we find that any nonzero fraction of dimers introduces finite dislocation cages, suggesting that glassy dynamics are present for any mixed crystal. However, we have also identified a vacancy-mediated uncaging mechanism for releasing dislocations from their cages. This mechanism is dependent on vacancy diffusion, which slows by orders of magnitude as the dimer concentration is increased. We propose that in mixed crystals with low dimer concentrations vacancy diffusion is fast enough to uncage dislocations and delay the onset of glassy dislocation dynamics. © 2010 The American Physical Society.

Citation

Gerbode SJ, Ong DC, Liddell CM, Cohen I (2010) Dislocations and vacancies in two-dimensional mixed crystals of spheres and dimers. Phys Rev E 82. Available: http://dx.doi.org/10.1103/PhysRevE.82.041404.

Acknowledgements

We thank Jim Sethna, Stefano Zapperi, Fernando Escobedo, Umang Agarwal, Carl Franck, Stephanie Lee, Erin Riley, and the Cohen group for helpful discussions. This research was supported in part by the Department of Energy, Basic Energy Sciences, Grant No. ER46517 (fabrication of colloidal assemblies and manipulation with optical trap) and in part by Award No. KUS-C1-018-02 from King Abdullah University of Science and Technology (KAUST).