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Modulus--Pressure Equation for Confined Fluids



Daniel W. Siderius, Gennady Y. Gor, Vincent K. Shen, Noam Bernstein


Ultrasonic experiments allow one to measure the elastic modulus of bulk solid or fluid samples. Recently such experiments have been carried out on fluid-saturated nanoporous glass to probe the modulus of a confined fluid. In our previous work (J. Chem. Phys., 2015, 143, 194506), using Monte Carlo simulations we showed that the elastic modulus $K$ of a fluid confined in a mesopore is a function of the pore size. Here we focus on modulus-pressure dependence $K(P)$, which is known to be linear for bulk materials, a relation known as the Tait-Murnaghan equation. Using transition-matrix Monte Carlo simulations we calculated the elastic modulus of bulk argon and confined in silica mesopores as a function of Laplace pressure. Our calculations show that while the elastic modulus is strongly affected by confinement and temperature, the slope of the modulus- pressure relation is not. Moreover, the calculated slope is in a good agreement with the reference data for bulk argon and experimental data for confined argon derived from ultrasonic experiments. We propose to use the value of the slope of $K(P)$ as a constraint to the analysis of experimental ultrasonic data, to estimate the elastic moduli of an unknown porous medium.
Journal of Chemical Physics


bulk modulus, confined fluid, adsorption, molecular simulation, thermodynamics, statistical mechanics


Siderius, D. , Gor, G. , Shen, V. and Bernstein, N. (2016), Modulus--Pressure Equation for Confined Fluids, Journal of Chemical Physics, [online], (Accessed April 24, 2024)
Created October 28, 2016, Updated June 2, 2021