  In this thesis, we develop a simple model potential for polar molecules that
effectively and accurately represents the thermodynamics of dilute gases. This
potential models dipolar interactions, with a nonpolar spherical component, as
seen in Stockmayer (SM) molecules or diatomic molecules such as dipolar
Lennard-Jones molecules with two centers (2CLJ). Predictions based on this
model for the second virial coefficient for SM and 2CLJ fluids closely match
recent numerical results obtained by C. Vega et al. The model is employed to
predict the critical temperature of an SM fluid with a variable dipole moment,
as well as its equilibrium liquid-vapor properties. Finally, we apply this
model to real polar molecules. A notable feature of this work is its connection
between the shape of the potential profile and thermodynamic properties.
