Journal of the American Chemical Society, Vol.121, No.13, 3175-3184, 1999
First-principles ion-water interaction potentials for highly charged monatomic cations. Computer simulations of Al3+, Mg2+, and Be2+ in water
The concept of hydrated ion [M(H2O)(m)](n+) has been used to describe interactions of highly charged monatomic cations in water. Ab initio interaction potentials for Al3+, Mg2+ and Be2+ have been developed on the basis of that previously applied to the Cr3+ hydration study (Martinez et al. J. Chem. Phys. 1998, 109, 1445). Transferability of the different contributions to the intermolecular potentials that describe the interactions between the central cation and the first hydration shell, Mn+-(H2O)(I), and the hydrate with bulk water molecules, [M(H2O)(m)](n+)-(H2O)(bulk), have been examined. Results indicate that a reduced number of points (similar to 40 quantum chemical computations) are enough to get the basic and differential features of each cation. MD simulations (200 ps) for the hydrate of each cation plus 512 TIP4P H2O have been performed. Structural properties such as RDFs among different pairs of atoms in the system and orientational parameter are presented. Likewise, dynamical properties such as self-diffusion coefficients, reorientational and mean residence times, and power spectra have been obtained and analyzed. The comparative study of the properties derived from the hydration of each cation and the degree of transferability of the intermolecular potentials based on their main features is thoroughly discussed. Prospectives and benefits introduced by this type of flexible hydrated ion-water interaction potential in molecular simulations are pointed out.