On the effective interaction of test multipoles in polar fluids

Abstract

An exact formula for the effective interaction energy of two test multipoles of arbitrary order immersed in a fluid of polar nonpolarizable molecules is derived. Coordinate space as well as Fourier space techniques are used. This allows for a careful specification of the range of validity of the results, which turn out to be rather general. The explicit dependence of the results on key parameters involved in microscopic dipole–dipole and dipole–multipole interactions is obtained, and a physical interpretation of these parameters is proposed.