ENERGY-DENSITY RELATIONSHIPS FOR THE TREATMENT OF ION SOLVATION WITHIN DENSITY-FUNCTIONAL THEORY

Useful energy-density relationships, connected with the embedding of s ingly charged postive or negative atomic ions in polar solvents, are d eveloped. The insertion of the atomic charged system into the polariza ble host is modeled through successive isoelectronic processes at the nucleus, involving a varying nuclear charge. In this way, the controve rsial procedure of selecting appropriate ionic radii, involved in the calculation of solvation energies through the Born formula, is avoided and replaced by integration in [0, infinity]. The approximate express ions, derived from a variational procedure proposed by Levy [J. Chem. Phys. 68, 5298 (1978); 70, 1573 (1979)], are reformulated within the n uclear-transition-state model. The classical reaction field expression for the insertion energy is recovered. The quality of the approximati ons made are discussed within the frame of the Kohn-Sham formulation o f density-functional theory.