Consequences of minimizing pair correlations in fluids for dynamics, thermodynamics, and structure

TL;DR

This study investigates how auxiliary pair interactions can suppress positional correlations in hard-sphere fluids, affecting their thermodynamics and dynamics, and explores the limits of pair disorder and stealthiness in fluid states.

Contribution

It introduces a method to suppress pair correlations in fluids using auxiliary interactions and analyzes the resulting thermodynamic and dynamic properties, revealing limits of pair disorder.

Findings

Suppression of pair correlations affects excess entropy and density fluctuations.

Maximized pair disorder correlates with increased stealthiness and fluid-like dynamics.

Incompressible, hyperuniform states can remain fluid-like without jamming.

Abstract

Liquid-state theory, computer simulation, and numerical optimization are used to investigate the extent to which positional correlations of a hard-sphere fluid--as characterized by the radial distribution function and the two-particle excess entropy--can be suppressed via the introduction of auxiliary pair interactions. The corresponding effects of such interactions on total excess entropy, density fluctuations, and single-particle dynamics are explored. Iso-g processes, whereby hard-sphere-fluid pair structure at a given density is preserved at higher densities via the introduction of a density-dependent, soft repulsive contribution to the pair potential, are considered. Such processes eventually terminate at a singular density, resulting in a state that--while incompressible and hyperuniform--remains unjammed and exhibits fluid-like dynamic properties. The extent to which static pair correlations can be suppressed to maximize pair disorder in a fluid with hard cores, determined via direct functional maximization of two-body excess entropy, is also considered. Systems approaching a state of maximized two-body entropy display a progressively growing bandwidth of suppressed density fluctuations, pointing to a relation between "stealthiness" and maximal pair disorder in materials.