Ab initio molecular dynamics simulations of Aluminum solvation

The solvation of Al3+ and its hydrolyzed species in water clusters has been studied by means of ab initio molecular dynamics simulations. The hexa-hydrate Al(H2O) 3+ 6 ion formed a stable complex in the finite temperature cluster simulation of one aluminum ion and 16 waters. The average dipole moment of strongly polarized hydrated water molecules in the first solvation shell of Al(H2O) 3+ 6 was found to be 5.02 Debye. The deprotonated Al(H2O)2(OH) − 4 complex evolves into a tetra-coordinated Al(OH)−4 aluminate ion with two water molecules in the second solvation shell forming hydrogen bonds to the hydroxyl groups in agreement with the observed coordination. At high temperature and for low water coordination protons in the first solvation shell are very mobile leading to the formation of hydrolysis species consistent with the acidity of Al3+ in water.