Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The initial part of this work is concerned with the construction and validity of model potential energies while the second part involves the use of statistical mechanical perturbation theory to evaluate some of the bulk properties of liquids for various types of potential models.;A previously developed potential model for isotropic intermolecular interactions is used for the construction of reliable potentials for interactions of unlike noble gas atoms. The potential model has essentially only one adjustable parameter which controls the balance between its exchange and Coulomb energy components. The parameters in the model potentials are determined by fitting second virial coefficient data. Generally, the approach leads to potentials of accuracy comparable to the best literature potentials which are usually based on a large base of experimental and/or theoretical input data.;An examination of the validity and properties of the atom-atom (site-site) potential model for the interactions of homonuclear diatomic molecules is considered. The intermolecular partial wave expansion of the atom-atom potential is developed and used to study the convergence of the partial wave expansion as a function of partial wave order, intermolecular orientation and distance, and the aniostropy of the interacting molecules. In marked contrast to previous work it is found that many of higher order partial work components are important relative to the isotropic term even for the interaction of relatively spherical molecules. The validity of the atom-atom potential as a separation of the correct intermolecular potential is also discussed in some detail.;Applications of the Fischer and RAM perturbation theories are made using some model potentials for the N(,2)-N(,2) interaction. Of particular importance is the study of the effects of various parts of a quantum mechanically realistic ab initio potential on calculated liquid properties. It is found that the contributions from the anisotropic part of the potential to the thermodynamic functions of liquid N(,2) are larger than previous estimates. The deviations of predicted liquid properties for the ab initio potential from experimental data are within the limits set by the estimated uncertainties, which can be substantial, of the ab initio calculations.



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