UBC Theses and Dissertations
The statistical mechanical theory of homonuclear diatomic fluids with application to liquid nitrogen Tam, Frank Wai-ming
The purpose of this thesis is to set up a basic theoretical scheme which will enable us to study the thermodynamic and structural properties of homonuclear diatomic fluids. We consider so-called interaction-site models which assume that the pair potential can be written as a sum of atom-atom interactions of the Lennard-Jones type. The pair potential is then expanded and expressed as a series in rotational invariants. This allows the short-ranged anisotropic forces and the long-ranged multipolar interactions to be treated in a unified manner. It is found that for nitrogen-like particles the expanded potential gives an accurate representation of the full pair interaction in the physically interesting range. The statistical mechanical theory we consider is based upon distribution function methods and employs integral equation techniques. We develop a general formulation and solve the relatively simple linearized hypernetted-chain (LHNC) approximation for a fluid of nitrogen-like particles. The structural properties predicted by the LHNC theory are in qualitative agreement with computer simulations, but rather poor results are obtained for some thermodynamic properties. Finally, some suggestions are made as to how the present theory might be improved and extended in future work.
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