(78c) Compressibility of Confined Fluid and Its Dependence on Pressure
Here we focus on the pressure dependence of the modulus. For bulk materials, this relationship is linear over a wide range of pressures and is known as the Tait-Munaghan equation. Using transition matrix Monte Carlo simulations  we calculated the isothermal modulus of bulk argon and confined in silica mesopores of various sizes. Our calculations show that although the elastic modulus itself is strongly affected by confinement, the slope of the Tait-Murnaghan equation is not, and is practically a universal thermodynamic property of a fluid. In addition to revealing a new fundamental regularity for confined fluids, our results provide additional information which can be applied for the analysis of experimental ultrasonic data, and allows one to estimate the elastic parameters of an unknown porous medium.
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