Monte Carlo simulation of growth of hard-sphere crystals on a square pattern

TL;DR

This study uses Monte Carlo simulations to analyze the growth and defect dynamics of hard-sphere colloidal crystals on a patterned substrate, revealing defect reduction and tetrahedral structure formation.

Contribution

It extends previous simulations by replacing boundary stress with patterned substrate stress, demonstrating defect disappearance and detailed defect behavior in colloidal epitaxy.

Findings

Disappearance of stacking faults under patterned conditions

Smooth sinking of the center of gravity with single relaxation mode

Formation of stacking fault tetrahedra observed in snapshots

Abstract

Monte Carlo simulations of the colloidal epitaxy of hard spheres (HSs) on a square pattern have been performed. This is an extension of previous simulations; we observed a shrinking intrinsic stacking fault running in an oblique direction through the glide of a Shockley partial dislocation terminating its lower end in fcc (001) stacking [Mori et al., Molec. Phys. 105 (2007) 1377], which was an answer to a question why the defect in colloidal crystals reduced by gravity [Zhu et al., Nature 387 (1997) 883]. We have resolved one of shortcomings of the previous simulations; the driving force for fcc (001) stacking, which was stress from a small periodic boundary simulation box, has been replaced with the stress from a pattern on the bottom. We have observed disappearance of stacking fault in this realizable condition. Sinking of the center of gravity has been smooth and of a single relaxation mode under the condition that the gravitational energy mgd is slightly less than the thermal energy kT. In the snapshots tetrahedral structures have appeared often, suggesting formation of staking fault tetrahedra.