Restricted Dislocation Motion in Crystals of Colloidal Dimer Particles

TL;DR

This study investigates how dislocation motion in colloidal dimer crystal monolayers is hindered by particle orientations, revealing unique defect interactions and potential differences from spherical crystal behaviors.

Contribution

It uncovers the restriction of dislocation glide due to particle orientations in colloidal dimer crystals and quantifies obstacle spacing and defect reaction mechanisms.

Findings

Dislocation glide is blocked by certain particle orientations.

Average obstacle spacing is approximately 4.6 lattice constants.

Dislocation reactions enable propagation beyond obstacles.

Abstract

At high area fractions, monolayers of colloidal dimer particles form a degenerate crystal (DC) structure in which the particle lobes occupy triangular lattice sites while the particles are oriented randomly along any of the three lattice directions. We report that dislocation glide in DCs is blocked by certain particle orientations. The mean number of lattice constants between such obstacles is 4.6 +/- 0.2 in experimentally observed DC grains and 6.18 +/- 0.01 in simulated monocrystalline DCs. Dislocation propagation beyond these obstacles is observed to proceed through dislocation reactions. We estimate that the energetic cost of dislocation pair separation via such reactions in an otherwise defect free DC grows linearly with final separation, hinting that the material properties of DCs may be dramatically different from those of 2-D crystals of spheres.