ORTHOGONAL POLYNOMIAL APPROACH TO FLUIDS WITH INTERNAL DEGREES OF FREEDOM - THE CASE OF NONPOLAR, POLARIZABLE MOLECULES

The molecules of real liquids have internal degrees of freedom that ma y couple with the external ones of position and orientation so that th ey affect and are affected by the microscopic liquid structure. For ca ses where the internal coordinates possess a Boltzmann-like distributi on, a procedure is described whereby such coordinates can be incorpora ted into the conventional formulation of classical liquid theory with no approximations beyond some reliable closure relation familiar from simple liquids. The basis of the procedure is expansions in appropriat e orthogonal polynomials of the internal coordinates. This program is successfully carried out for a classical model of nonpolar, polarizabl e molecules treated as Drude oscillators, generalizing published solut ions of the mean spherical approximation for the same model.