Polarizabilities of hydrated and free ions derived from DFT calculations

Geometries, static dipole polarizabilities, ionization energies, and dipole moments of small ionic and a few uncharged species have been derived from density functional theory (DFT) (aug-cc-pV5Z) zero-temperature calculations. Both cases of hydrated and gas phase species are reviewed. For the two test cases, Na+ and Cl-, different methods for including solvent effects [polarizable continuum model (PCM), supermolecule, charge distribution, semi-continuum] are reviewed, showing pronounced differences in the results for the polarizabilities. While pure PCM calculations tend almost always to increase the polarizabilities with respect to the gas phase values, methods mimicking the surrounding solvent by point charge distributions usually give smaller values. Semi-continuum calculations include both polarization effects of the medium as well as electronic confinement due to electrostatic repulsion. It remains a challenge to incorporate such polarizabilities into either classical molecular mechanics simulations or analytical theories of ionic solutions in an unambiguous and accurate fashion. (C) 2006 Wiley Periodicals, Inc.