The thermodynamic and structural effects of highly anisotropic, short-ranged
attraction are investigated for single- and four-site interaction models using
Wertheim's multi-density graph theory of chemical association. Both models consist
of associating hard spheres, where the saturable attraction sites are described
by conical wells centered in the hard core and evaluated in the "sticky-spot" limit.
The resulting fluids then mimic many of the directional and steric-constrained
properties of hydrogen-bonded fluids.
The single-site model is used to explore the effects of dimerization upon
the well-known properties of a planar liquid-vapor interface. Apart from hard
sphere repulsion and sticky-spot attraction, a van der Waals-like dispersion interaction
is incorporated to generate the critical point. Association is treated within
Wertheim's thermodynamic perturbation theory, along with classical density functional
methods to determine the interfacial density profile. The direct correlation
functions which carry all bonding information are derived by means of the
associative Ornstein-Zernike equations with a Percus-Yevick-like closure relation.
The primary effects of dimerization are manifest in system thermodynamics. Critical
temperatures and densities are shifted from their non-associating values and
small, non-monotonic shifts in the correlation length and surface tension are also
observed. While these effects are accompanied by interface compositional changes,
any influence upon the density profile seems to be subsumed by use of the proper
T/T[subscript c].
The four-site, network-forming model is investigated as a prototype for the
thermodynamics and structural properties of water. Bonding interactions occur
between "hydrogen" and electron "lone pair" sites described in the sticky-spot
limit. System properties are derived under the ideal network approximation using
the same methods as for the one-site model and are found to qualitatively reproduce
some thermodynamic and connectivity features characteristic of real water.
Partial densities are calculated self-consistently within the theory, and most thermodynamic
quantities can be written in terms of the average number of hydrogen
bonds per molecule. An analytical structure factor is also derived for this model. / Graduation date: 2003
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/31171 |
| Date | 20 May 2003 |
| Creators | Peery, Travis B. |
| Contributors | Evans, Glen T. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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