Hirshfeld density partitioning technique: a first application to the transition metal compounds, HScO, TiO, VO.

We apply a variant of the Hirshfeld density partitioning technique, HI, to calculate the atomic charges and decompose the dipole moments into the part due to the charges and the induced dipoles developed on each atom for three different transition metal (TM) containing molecules. Additionally, the α and β spin densities are treated separately developing a new variant (spin-adapted HI) of the fractional occupation HI version proposed recently. We also study the dependence of HI charges on the atomic state of the TM employed in the promolecule. The VO case exhibits a strong dependence of the atomic charge on the V or V(+) state used. Although the bonding in the ground high spin electronic state and the first excited low spin state in TiO and VO is essentially identical, the dipole moments differ significantly and we find that this is due entirely to the σ electron distribution localized on the transition metal. Finally, the mechanism for the rapid change of the dipole moment of HScO upon bending is confirmed to occur mainly due to the induced atomic charges.