Measuring nonlinear stresses generated by defects in 3D colloidal crystals

TL;DR

This paper presents direct measurements of nonlinear stresses around defects in 3D colloidal crystals, revealing how these stresses influence defect interactions and material properties, with implications for understanding transport, strain hardening, and fatigue.

Contribution

It introduces a novel experimental approach to measure nonlinear stresses around defects in colloidal crystals, providing new insights into defect interactions and stress distributions.

Findings

Vacancy cores generate attractive interactions.

Crystalline regions soften around dislocation cores.

Stress fluctuations are uniformly distributed in polycrystals.

Abstract

The mechanical, structural and functional properties of crystals are determined by their defects and the distribution of stresses surrounding these defects has broad implications for the understanding of transport phenomena. When the defect density rises to levels routinely found in real-world materials, transport is governed by local stresses that are predominantly nonlinear. Such stress fields however, cannot be measured using conventional bulk and local measurement techniques. Here, we report direct and spatially resolved experimental measurements of the nonlinear stresses surrounding colloidal crystalline defect cores, and show that the stresses at vacancy cores generate attractive interactions between them. We also directly visualize the softening of crystalline regions surrounding dislocation cores, and find that stress fluctuations in quiescent polycrystals are uniformly distributed rather than localized at grain boundaries, as is the case in strained atomic polycrystals. Nonlinear stress measurements have important implications for strain hardening, yield, and fatigue.