INCORPORATION OF REACTION FIELD EFFECTS INTO DENSITY-FUNCTIONAL CALCULATIONS FOR MOLECULES OF ARBITRARY SHAPE IN SOLUTION

An attempt is made to combine continuum reaction field approaches with DFT ab initio calculations for quantitative evaluation of solvation e ffects in chemical processes. The formalism of the combined method is delineated along with its possibilities and limitations, and applied t o several small model systems. It is found that DFT can provide dipole moments in vacuum and in solution (e.g., for water) with accuracies ( 0.1 D) that have not been reported with other methods. The results obt ained suggest that agreement within similar to 1 kcal/mole can be expe cted between calculated and experimental hydration enthalpies of polar uncharged solutes. The results for ions are not as consistent as for dipolar molecules, suggesting that accurate multipole representations of the electron density of solutes may be required especially for ioni c solutes.