From molecules to thermophysical properties: Applications of ab initio and molecular simulation methods.

摘要

The concept that the simple knowledge of the molecular structure is all the needed information to predict the behavior and equilibrium properties of any system is the philosophy of this dissertation. By combining computational chemistry tools, both ab initio methods and molecular simulations, a complete and rigorous description of molecular interactions are determined that lead to the understanding of molecular behavior and the prediction of the thermophysical properties from a small number or a large ensemble of molecules. All the studies presented here are founded on the framework of quantum chemistry to define, without any approximations, molecular interactions.; To demonstrate the usefulness of quantum chemistry and its combination with statistical mechanics for equilibrium properties predictions, three separate studies, but with the same underlying philosophy, are presented in this dissertation. The first is the use of quantum chemical methods to determine interaction energies between the like and unlike components in a molecular cluster, so these can the be used as parameters in excess free energy models. In the second study of this dissertation, ab initio pair potentials and molecular simulations are combined to determine their ability to predict phase equilibria properties. Ab initio potentials are obtained from the calculation of interaction energy for several hundreds of configurations between a pair of molecules, which are then used to develop a site-site pair potentials to describe the intermolecular interactions. In this dissertation, the ab initio pair potentials are used in Gibbs Ensemble Monte Carlo simulations to predict the phase behavior of pure components and a mixture. In the last part of this dissertation, the cooperativity effect in hydrogen-bonding systems is examined by quantum chemical means to obtain a quantitative description that clearly identifies the effects associated with this effect.; The studies reported in this dissertation show a few selected aspects of using computational chemistry, both quantum chemistry and molecular simulations, in areas of practical interest to engineers, chemists, and physicists. It is hoped that this work will lead to further engineering applications combining quantum chemistry and molecular simulations for better understanding of molecular interactions and predictions of macroscopic properties.