A generalized formulation of the electronegativity equalization principle is presented from the perspective of density-functional theory. The resulting equations provide a linear-response framework for describing the redistribution of electrons upon perturbation by an external density or applied field. The equations can be solved using a finite set of basis functions to model the density response. Applications demonstrate the method accurately reproduces dipole moments and chemical potentials obtained from density-functional calculations. The method provides high accuracy in the presence of relatively strong perturbations such as those arising from interactions with other molecules or applied fields, and is “exact” in the limit that these interactions vanish. The method has the advantage that accuracy can be systematically improved by inclusion of more complete basis functions. The present formulation provides the foundation for a promising semiempirical model for polarization and charge transfer in molecular simulations.
