Calculation by analytical and local-density Hartree–Fock methods of spin and charge densities in the VII hexaaqua ion

Abstract

Calculations on a V(OH₂)²⁺₆ ion in the experimental geometry have been performed with conventional ab initio and with discrete-variational local-density functional approximation unrestricted Hartree–Fock methods. In each case a variety of basis sets was employed. The charge and spin distributions produced were compared with each other, and the latter with experimental results from a polarized neutron diffraction experiment on (ND₄)₂V(SO₄)₂ 6D₂O. If the DZP ab initio results are taken as the benchmark, the charge-difference and the spin-density maps of the LDF methods are in good agreement, certainly within the errors associated with the relevant experiments. However, when Mulliken population analyses are performed, rather different results are obtained from different basis sets and methods, and this emphasizes the difficulty of comparing theoretical atomic orbital populations with those obtained by least-squares modelling of the experimental data.