On the dielectric constant of non-polar fluids

The deviation from the Clausius-Mossotti equation predicted by a theory of dielectric response which consistently includes molecular quadrupoles and intermolecular field gradients is examined in the form of a virial series. The configurational integrals required are evaluated analytically for the hard sphere and square well fluids. The results are compared with existing theoretical results, in the dipoles only approximation, for the hard sphere and Lennard-Jones fluid. The requisite molecular properties for argon have been determined from ab initio calculations. For this case it is shown that the induced quadrupole terms constitute a considerable fraction (∼ 30 per cent) of the deviation predicted by the presently available theories. The relationship between the calculated values of the deviation for the square well fluid and the experimental values for argon is discussed at length.