Molecular dynamics simulations of Hg2+ in aqueous solution including N-body effects

Pair-potential, three-body corrected and combined ab initio quantum mechanics/molecular mechanics molecular dynamics (QM/MM-MD) simulations have been performed for Hg2+ in water. The ion's hydration structure was evaluated in terms of radial distribution functions, coordination numbers, and angular distributions, together with changes in ligand structure upon binding of water molecules. An octahedral solvate complex with coordination number of 6/22 for first/second shell results from QM/MM-MD simulations, with average Hg2+-O distance 2.42 A for the first shell. The pair-potential simulation gives strongly wrong results, the inclusion of three-body effects corrects many, but not all of the errors. The hydration enthalpy of -553+/-3 kcal/mol obtained from the QM/MM-MD simulation seems a reasonable value for dilute solution, when compared with experimental estimations. (C) 2003 American Institute of Physics.