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

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.