Semiclassical statistical theory and computer simulations of confined quantum fluids

Abstract

Among various alternative fuels to gasoline an diesel, hydrogen remains to be a very attractive alternative. Nowadays, several types of porous materials have been extensively studied and tested as potential candidates for storage of hydrogen. On the other hand, the evaluation of an adsorptive process is commonly based in new adsorptive materials nanoporous technologies and predictive models based on equations of state. The great importance of hydrogen, thinking as a green combustible, have increased the searching for more accurate predicting models of thermodynamic properties. Molecular simulations and theoretical approaches are of key importance because the prediction of the adsorption properties over a wide range of temperatures and pressures would reduce the number of time consuming experiments required for performance evaluations. This thesis presents a theoretical analysis of the adsorption of mixtures containing quatum fluids at high pressures and low temperatures. Computer simulations under the Metropolis Monte Carlo scheme and molecular equation of state was the main methodology used in this work. The thesis is integrated in three items: The first step is the development of a semiclassical approach to model quantum fluids using the Statistical Associating Fluid Theory for Potential of Variable Range (SAFT-VR), that can be used to determine thermodynamic properties of quantum fluids. This theory is applied to the prediction of liquid-vapor properties of fluids like molecular hydrogen, neon, deuterium and helium-4. To understand the behaviour of these fluids under connement and their adsorptive properties, in the second part of the thesis a MC simulation study of quantum fluids using semiclassical efective pair potentials is presented. The first and second parts are the basis for the development of a two-dimentional equation of state to predict adsorption isotherms of pure quantum fluids and mixtures of there onto different surface substrates. In all cases: theory, experimental data, and computer simulations were compared.