Relation Between Pore Size and the Compressibility of a Confined Fluid

TL;DR

This paper establishes a theoretical relation between pore size and the isothermal compressibility of confined argon, enabling pore size estimation from ultrasonic measurements.

Contribution

It introduces a simple relation linking pore size to compressibility of confined fluids, supported by simulation methods, aiding pore characterization.

Findings

Derived a relation between pore size and compressibility.

Validated the relation using grand-canonical Monte Carlo simulations.

Proposed a method to estimate pore sizes from ultrasonic measurements.

Abstract

When a fluid is confined to a nanopore, its thermodynamic properties differ from the properties of a bulk fluid, so measuring such properties of the confined fluid can provide information about the pore sizes. Here we report a simple relation between the pore size and isothermal compressibility of argon confined in these pores. Compressibility is calculated from the fluctuations of the number of particles in the grand canonical ensemble using two different simulation techniques: conventional grand-canonical Monte Carlo and grand-canonical ensemble transition-matrix Monte Carlo. Our results provide a theoretical framework for extracting the information on the pore sizes of fluid-saturated samples by measuring the compressibility from ultrasonic experiments.