APPLICATION OF THE HYDRATED ION CONCEPT FOR MODELING AQUEOUS-SOLUTIONS CONTAINING HIGHLY-CHARGED IONS - A MONTE-CARLO SIMULATION OF CR3-INITIO INTERMOLECULAR POTENTIAL( IN WATER USING AN AB)

An interaction potential between the hydrated ion, [Cr(H2O)(6)](3+), a nd a water molecule has been developed starting from restricted open-s hell Hartree-Fock (ROHF) ab initio calculations using DZV basis sets. The importance of many-body effects associated with this potential is examined up to the level of a cluster including the second hydration s hell. Monte Carlo simulations of Cr3+ aqueous solutions using this pot ential for hydrated ion-solvent interactions and the MCY for water-wat er interactions have been performed. The influence of the number of wa ter molecules employed for simulations has been examined by performing simulations with 210 and 512 water molecules. Structural results deri ved from simulations indicate a well-defined second hydration shell. T he Cr-O and Cr-H radial distribution functions (RDFs) show maxima arou nd 4.06 and 4.49 Angstrom, giving integration numbers of similar to 14 and 36, respectively. Evidence of a diffuse third hydration shell is also shown by the Cr-O RDF. The Cr3+ hydration energy is slightly over estimated with respect to the experimental value. Advantages and limit ations of the hydrated ion approach in computer simulations are discus sed.