Particle displacements in the elastic deformation of amorphous materials: local fluctuations vs. non-affine field

TL;DR

This paper investigates local particle displacements in amorphous materials, distinguishing between continuous deformation and localized fluctuations, and introduces a scalar 'noise' field to better model localized irreversible events.

Contribution

It introduces a decomposition of particle displacements into a smooth field and localized fluctuations, highlighting the small, system size independent correlation length of fluctuations and proposing a new scalar 'noise' field for modeling.

Findings

Fluctuations are highly localized with a correlation length of about a particle diameter.

The non-affine field differs from fluctuations, being less localized.

The scalar 'noise' field effectively characterizes localized irreversible events.

Abstract

We study the local disorder in the deformation of amorphous materials by decomposing the particle displacements into a continuous, inhomogeneous field and the corresponding fluctuations. We compare these fields to the commonly used non-affine displacements in an elastically deformed 2D Lennard-Jones glass. Unlike the non-affine field, the fluctuations are very localized, and exhibit a much smaller (and system size independent) correlation length, on the order of a particle diameter, supporting the applicability of the notion of local "defects" to such materials. We propose a scalar "noise" field to characterize the fluctuations, as an additional field for extended continuum models, e.g., to describe the localized irreversible events observed during plastic deformation.