Structural arrangement and dynamics of the hydrated Mg2+: An ab initio QM/MM molecular dynamics simulation

The structural arrangement and dynamics of solvated Mg2+ in dilute aqueous solution have been studied by ab initio QM/MM molecular dynamics simulation, in which the whole first and most of the second hydration shell of the ion were treated at Hartree–Fock level using LANL2DZ basis sets. Besides the most stable Mg2+(H2O)6 species, intermediates such as Mg2+(H2O)5(H2O), where at least one water molecule temporarily moves into the inter-shell region but remains H-bonded to inner-shell water, as well as transition complexes of the Mg2+(H2O)6(H2O) type, exist in aqueous solution. The dynamics of solvate and surrounding water molecules are discussed in connection to the ‘structure-forming’ ability of Mg2+.