Calculating interaction energies in transition metal complexes with local electron correlation methods.

The results of density fitting and local approximations applied to the calculation of transition metal–ligand binding energies using second order Mo\ller–Plesset perturbation theory are reported. This procedure accurately reproduces counterpoise corrected binding energies from the canonical method for a range of test complexes. While counterpoise corrections for basis set superposition error are generally small, this procedure can be time consuming, and in some cases gives rise to unphysical dissociation of complexes. In circumventing this correction, a local treatment of electron correlation offers major efficiency savings with little loss of accuracy. The use of density fitting for the underlying Hartree–Fock calculations is also tested for sample Ru complexes, leading to further efficiency gains but essentially no loss in accuracy. [ABSTRACT FROM AUTHOR]