Classical and QM/MM molecular dynamics simulations of Co2+ in water

Classical and quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations have been performed to describe structural and dynamical properties of Co2+ in water. The most important region, the first hydration shell, was treated by ab initio quantum mechanics at unrestricted Hartree-Fock (UHF) level using the LANL2DZ ECP basis set for Co2+ and the double-zeta plus polarization basis set for water. For the rest of the system newly constructed three-body corrected potential functions were used. A well-structured rigid octahedron was observed for the stable first hydration shell showing no first shell water exchange process within a simulation time of 11.9 ps. For second hydration shell ligands, a mean residence time of 28 ps was observed. Librational and vibrational motions as well as the ion-oxygen motion were investigated by means of velocity autocorrelation functions showing significant differences between classical and QM/MM results. (C) 2003 Elsevier B.V. All rights reserved.