Statistical mechanics of homogeneous partly pinned fluid systems

TL;DR

This paper explores the configurational properties of homogeneous partly pinned fluid systems, revealing a complementarity between mobile and immobile phases, and deriving identities that simplify structural analysis in simulations and theory.

Contribution

It introduces a novel analysis of the configurational properties of partly pinned fluid systems, highlighting a complementarity and deriving identities that facilitate structural computations.

Findings

Identifies a complementarity between mobile and immobile phases.

Derives identities linking different configurational averages.

Simplifies structural quantity calculations in simulations and theory.

Abstract

The homogeneous partly pinned fluid systems are simple models of a fluid confined in a disordered porous matrix obtained by arresting randomly chosen particles in a one-component bulk fluid or one of the two components of a binary mixture. In this paper, their configurational properties are investigated. It is shown that a peculiar complementarity exists between the mobile and immobile phases, which originates from the fact that the solid is prepared in presence of and in equilibrium with the adsorbed fluid. Simple identities follow, which connect different types of configurational averages, either relative to the fluid-matrix system or to the bulk fluid from which it is prepared. Crucial simplifications result for the computation of important structural quantities, both in computer simulations and in theoretical approaches. Finally, possible applications of the model in the field of dynamics in confinement or in strongly asymmetric mixtures are suggested.