REVALUATION OF THE LOCAL FIELD

Rigorous formulation of macroscopic fields through cell averages of microscopic fields and strict avoidance of self-interaction make a derivation of the local field possible through surface integrals over just one molecular cell in contrast to the traditional cavity method. As an example we present the local field for an orthorhombic cell in terms of analytical geometry factors. An analysis of approximations permits a reevaluation of the cavity method. The Lorentz formula for a cubic cell, Eloc = E + ( 4π 3)P, is found to be accurate to second order. The wide-spread belief that the difference between the local field and the Maxwell field arises from dipoles near the molecule under consideration must be repudiated as a misconception. We show that this field difference originates solely from the self-field of the charge distribution in the molecular cell. © 1990.