  It is shown that the errors of present-day exchange-correlation (xc)
functionals are rather short ranged. For extended systems the correction can
therefore be evaluated by analyzing properly chosen clusters and employing
highest-quality quantum chemistry methods. The xc correction rapidly approaches
a universal dependence with cluster size. The method is applicable to bulk
systems as well as to defects in the bulk and at surfaces. It is demonstrated
here for CO adsorption at transition-metal surfaces, where present-day xc
functionals dramatically fail to predict the correct adsorption site, and for
the crystal bulk cohesive energy.
