Octahedral structure of Al3+ (aq.)
We start our ab initio molecular dynamics investigations by placing one aluminum ion (blue) into the middle of the cluster of randomly oriented 16 water molecules in a cubic simulation box with a length of 20 a.u.
On the time scale of about 0.25 ps, dramatic rearrangement of water cluster took place with the formation of an almost perfect octahedra complex of Al(H2O)63+ surrounded by 10 remaining water molecules.
This octahedral structure appears to be very stable and remained intact during the consequent 1 ps run at ambient conditions.
Ab initio molecular dynamics of aluminum solvation
by Mark I. Lubin and John H. Weare, UCSD