Influence of inherent structure shear stress of supercooled liquids on their shear moduli

TL;DR

This paper explores how inherent structure shear stress in supercooled liquids, influenced by boundary conditions, affects the calculation of shear moduli, revealing non-thermal contributions and size dependence.

Contribution

It provides a detailed analysis of the boundary condition effects on inherent structure shear stress and its impact on shear modulus calculations in supercooled liquids.

Findings

IS stress supports non-zero shear stress in inherent structures

Boundary conditions influence the IS stress and shear modulus calculations

Proper correction for IS stress prevents unphysical divergence of moduli at low temperatures

Abstract

Configurations of supercooled liquids residing in their local potential minimum (i.e. in their inherent structure, IS) were found to support a non-zero shear stress. This IS stress was attributed to the constraint to the energy minimization imposed by boundary conditions, which keep size and shape of the simulation cell fixed. In this paper we further investigate the influence of these boundary conditions on the IS stress. We investigate its importance for the computation of the low frequency shear modulus of a glass obtaining a consistent picture for the low- and high frequency shear moduli over the full temperature range. Hence, we find that the IS stress corresponds to a non-thermal contribution to the fluctuation term in the Born-Green expression. This leads to an unphysical divergence of the moduli in the low temperature limit if no proper correction for this term is applied. Furthermore, we clarify the IS stress dependence on the system size and put its origin on a more formal basis.