Point Defect Dynamics in Two-Dimensional Colloidal Crystals

TL;DR

This study investigates the movement and behavior of point defects in 2D colloidal crystals using simulations, revealing distinct diffusion mechanisms and pathways for vacancies and interstitials, with experimental validation for vacancies.

Contribution

It introduces detailed simulation-based insights into the topological defect dynamics in 2D colloidal crystals, including new diffusion pathways for interstitial defects.

Findings

Vacancy defects glide and rotate along lattice directions.

Interstitial defects exhibit additional diffusion pathways.

Interstitials are more mobile than vacancies.

Abstract

We study the topological configurations and dynamics of individual point defect vacancies and interstitials in a two-dimensional colloidal crystal. Our Brownian dynamics simulations show that the diffusion mechanism for vacancy defects occurs in two phases. The defect can glide along the crystal lattice directions, and it can rotate during an excited topological transition configuration to assume a different direction for the next period of gliding. The results for the vacancy defects are in good agreement with recent experiments. For the interstitial point defects, which were not studied in the experiments, we find several of the same modes of motion as in the vacancy defect case along with two additional diffusion pathways. The interstitial defects are more mobile than the vacancy defects due to the more two-dimensional nature of the diffusion of the interstitial defects.