APPLICATIONS OF QUANTUM CHEMISTRY TO METAL COMPLEXES IN AQUEOUS SOLUTIONS

APPLICATIONS OF QUANTUM CHEMISTRY TO METAL COMPLEXES IN AQUEOUS SOLUTIONS 

In this section, we will review some of the recent applications of both density functional and Hartree-Fock based calculations to metal complexes of geochemical interest. High-level calculations on small clusters representing a metal cation with its first and, and possibly second, coordination shell allow us to predict spectroscopic properties (see Tossell, this volume) and this can be of great utility interpreting experimental data. Moreover, if we are able to adequately model the solvation environment, we can predict the thermodynamic stabilities of different metal complexes. First-principles calculations on small clusters can be used to derive interatomic potentials that can be used in classical molecular dynamical simulations (next section) of aqueous solutions as a function of pressure, temperature and composition. Examples of such simulations will be given below. 

A natural starting point is the simple aquo complexes of Zn, Cd and Hg. Calculated structures and formation energies Ehyd) of the hexa-aquo complexes from both density functional (Sherman, unpublished  

References Ohtaki et al. 1976 Shapovalov and Radchenko 1971 tossell 1991 Aotton and Wilkinson 1988 Mhtaki et al. 1974 Mosselmans et al. 19% Butterworth et al. 1992 abata and Ozutsumi 1992 Stromberg et al. 1990 

The Raman spectrum of the Cd aquo complex has been measured and calculated by Rudolph and Pye (1998) at the Hartree-Fock + MP2 level of theory. Calculated Cd-0 vibrational modes were 16% lower than experiment in the Cd(H20)6 cluster but in good agreement with experiment using a cluster including the second solvation shell Cd(H20)6(H20)l2  

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