The Structural Features of the Hydrated Ferrous Ion Clusters: [Fe(H2O) n ]2+ (n = 1–19)

Abstract

The low-lying structures of the hydrated ferrous ion clusters [Fe(H2O) n ]2+ (n = 1–19) were extensively searched at the level of the density functional theory. The results show that the first hydration shell consists of six water molecules, and the second hydration shell contains seven water molecules. Furthermore, it is found that all the lowest-energy states of [Fe(H2O) n ]2+ (n = 1–19) clusters are spin quintet states. These lowest-energy states keep well even at finite temperatures. The analyses of the successive water binding energy and natural charges population on ferrous ion clearly show that the influence of ferrous ion on the surrounding water molecules goes beyond the second hydration shell.