Calculated lanthanide contractions for molecular trihalides and fully hydrated ions: The contributions from relativity and 4f-shell hybridization

The contribution of relativistic effects to the lanthanide contraction of chemical bonds from La to Lu is calculated for realistic systems. Pronounced participation of the 4f shell to the bonding is found for one case, LuF3, contrary to the usual expectations. Large lanthanide nuclear quadrupole constants are predicted for the molecular trihalides.