Multipolar theory of dielectric polarization in dense mixtures

Abstract

By statistical mechanics and a multipole tensor formalism, an expression for the dielectric polarization of dense mixtures is derived, of such generality as to account for certain new factors of a molecular nature not taken into account in hitherto-existing theories. The general results are discussed in some special cases of dipolar, quadrupolar, octopolar, etc. systems and applied to moderately dense gases, in which the second dielectric virial coefficient provides the basis for determining molecular multipole moments or multipole polarizabilities of order higher than dipolar. This indirect method yields a quadrupole moment of 5 × 10-26 e.s.u. cm2 for the CO2 molecule and an octopole moment of 4 × 10-34 e.s.u. cm3 for the CH4 molecule.