Calculations of hydrated titanium ion complexes: structure and influence of the first two coordination spheres

Density-functional studies of titanium cation complexes with 6 and 18 water molecules were carried out. The charges +2, +3 and +4 were all considered. The lowest-energy minimum of the trivalent hexahydrated cation may have S6 symmetry. The inclusion of the second coordination sphere leads to two geometrically distinct types of minima. Hydration energies of the Ti2+ and Ti3+ are calculated with 13–86 kJ/mol accuracy. The hydration energy of the Ti4+ ion is estimated at 7800 kJ/mol.