Accuracy of various approximations to exchange and correlation for the electron density distribution in atoms and small molecules

The general usefulness of various local and non-local approximations to the exchange-correlation potential in density functional theory is studied by comparing resulting electron density distributions to essentially exact results for light atoms. The correlation contribution to the electron density in CO and H2O is compared with CI results. It is concluded that density functional theory provides a viable alternative to HF and CI approaches for the calculation of deformation densities, although the response of the electron density to the correlation potential is only moderately accurate.