Fig. 1: Plastic relaxation and definition of strain measure.
From: Dislocation interactions during plastic relaxation of epitaxial colloidal crystals
a Particle stacking of {111} and {001} fcc planes. b Snapshots of a crystal growing on a flat substrate (unconstrained) show growth of columnar grains along the [111] direction. The crystal height and the direction of gravity are denoted by h and g, respectively. Grains are predominantly fcc (green) with hcp stacking faults (orange). Grain boundaries are marked by gray particles that are not identified with a crystalline structure. c Snapshots of a crystal growing on a [001] template. At h = 25 μm (c, left) the crystal is defect free. By the time the crystal reaches h = 40 μm (c, right) hcp stacking faults have formed. d, top Evolution of \({d}_{\parallel }^{0}\) and d∥, particle-particle distances in a plane parallel to the substrate, averaged over the crystal thickness, for crystals grown on a flat substrate and on a template, respectively (see panel a). The onset of relaxation is marked by a sharp decrease of d∥ as h reaches a critical thickness hc ≈ 26 μm. d, bottom Total (εtot) and elastic (εe) strains in constrained crystals, as defined in the main text. For h < hc imposed strains are accommodated elastically, εtot = εe, whereas for h > hc, relaxation is mediated by plastic strain, εp. The shadows denote the variation over five distinct observation regions of a growing crystal. Here, the ionic strength I = 2 mM and template spacing dt = 1.69(5) μm.
