Molecular Dynamics and X-Ray Diffraction Study of Aqueous Beryllium(II) Chloride Solutions

A structural investigation o f a 1.1 molal BeCl2 aqueous solution has been performed by a molecular dynamics simulation together with X-ray diffraction studies o f 1.1 and 5.3 molal BeCl2 aqueous solutions at pH = \. A central force model in combination with an improved intra­ molecular three-body potential was used for water. The ion-water and ion-ion potentials were derived from ab initio calculations. The structure function obtained from the simulation is in satisfactory agreement with that from X-ray diffraction. The M D simulation o f the 1.1 molal solution shows that the hydration shell o f Be2+ consists o f six water molecules occupying octa­ hedral sites around a central Be2+. The X-ray scattering data o f the 5.3 molal solution indicate that Be2+ has only four water molecules in the first hydration shell. The average coordination number o f Clis found to be about seven in the 1.1 molal solution from both X-ray diffraction and M D simulation, but C lis surrounded on the average by 3.4 water molecules in the 5.3 molal solution. The influence o f the small divalent Be2+ on the geometry o f its nearest neighbour water molecules is compared with the results o f previous simulations o f 1.1 molal MgCl2 and CaCl2 solutions.