Domain and Stripe Formation Between Hexagonal and Square Ordered Fillings of Colloidal Particles on Periodic Pinning Substrates

TL;DR

This study uses large-scale simulations to explore how colloidal particles arrange themselves on periodic pinning substrates, revealing diverse ordering patterns and boundary formations depending on particle filling levels.

Contribution

It demonstrates the ability to tailor grain boundary structures in colloidal assemblies using muffin-tin periodic pinning substrates, highlighting new ordering phenomena at various fillings.

Findings

Hexagonal order at four particles per site

Square order at five particles per site

Diverse regimes including grain boundaries and stripe structures

Abstract

Using large scale numerical simulations, we examine the ordering of colloidal particles on square periodic two-dimensional muffin-tin substrates consisting of a flat surface with localized pinning sites. We show that when there are four particles per pinning site, the particles adopt a hexagonal ordering, while for five particles per pinning site, a square ordering appears. For fillings between four and five particles per pinning site, we identify a rich variety of distinct ordering regimes, including disordered grain boundaries, crystalline stripe structures, superlattice orderings, and disordered patchy arrangements. We characterize the different regimes using Voronoi analysis, energy dispersion, and ordering of the domains. We show that many of the boundary formation features we observe occur for a wide range of other fillings. Our results demonstrate that grain boundary tailoring can be achieved with muffin-tin periodic pinning substrates.