Strain fields in repulsive colloidal crystals

Abstract

The concept of a local linear elastic strain field is commonly used in the metallurgical research community to approximate the collective effect of atomic displacements around crystalline defects. Here we show that the elastic strain field approximation is a useful tool in colloidal systems. For colloidal crystals with repulsive particle interaction potentials, given similar mechanical properties, sharper potentials lead to (1) free energies of deformation dominated by entropy, (2) lower variance in strain field fluctuations, (3) increased tension-compression asymmetry near dislocation core regions, and (4) smaller windows of applicability of the linear elastic approximation. We show that the window of linear behavior for entropic colloidal crystals is broadened for pressures at which the interparticle separation sufficiently exceeds the range of steep repulsive interactions.