The hydration energies of the proton, hydroxyl ion, and several inorga
nic ions were calculated using the multicavity self-consistent reactio
n held (MCa SCRF) method developed for the quantum-mechanical modeling
of rotationally or flexible systems in dielectric media. The ionic co
mplexes H3O+(H2O)(4), OH-(H2O)(4), NH4+(H2O)(4), and Hal(-)(H2O)(4), w
here Hal = F, Cl, or Br, have been studied. Each complex was divided b
etween five spheres, corresponding to the central ion and four water m
olecules in their first coordination sphere, respectively. Each cavity
was surrounded by a polarizable medium with the dielectric permittivi
ty of water at room temperature (80). The ionic hydration energies of
ions were divided into specific and nonspecific parts. After accountin
g for the cavity-formation energy using scaled particle theory, good a
greement between the total calculated and experimental hydration energ
ies was obtained for all ions studied. (C) 1994 John Wiley & Sons, Inc
.