Extracting the properties of quasilocalized modes in computer glasses: Long-range continuum fields, contour integrals and boundary effects

TL;DR

This paper develops a continuum theory and contour integral method to accurately extract the core properties of quasilocalized modes in computer glasses, accounting for boundary effects caused by finite system sizes and periodic boundary conditions.

Contribution

It introduces a novel contour integral approach combined with a continuum theory to isolate core properties of localized modes, correcting for boundary effects in simulations.

Findings

Boundary effects significantly alter long-range fields in finite systems.

The continuum theory accurately predicts boundary-induced field modifications.

The method successfully extracts intrinsic core properties in 2D and 3D simulations.

Abstract

Low-frequency nonphononic modes and plastic rearrangements in glasses are spatially quasilocalized, i.e. feature a disorder-induced short-range core and known long-range decaying elastic fields. Extracting the unknown short-range core properties, potentially accessible in computer glasses, is of prime importance. Here we consider a class of contour integrals, performed over the known long-range fields, which are especially designed for extracting the core properties. We first show that in computer glasses of typical sizes used in current studies, the long-range fields of quasilocalized modes experience boundary effects related to the simulation box shape and the widely employed periodic boundary conditions. In particular, image interactions mediated by the box shape and the periodic boundary conditions induce fields' rotation and orientation-dependent suppression of their long-range decay. We then develop a continuum theory that quantitatively predicts these finite-size boundary effects and support it by extensive computer simulations. The theory accounts for the finite-size boundary effects and at the same time allows the extraction of the short-range core properties, such as their typical strain ratios and orientation. The theory is extensively validated in both 2D and 3D. Overall, our results offer a useful tool for extracting the intrinsic core properties of nonphononic modes and plastic rearrangements in computer glasses.