The importance of fully quantitative non-local treatments of exchange energy in Density Functional Theory of atoms,molecules and clusters,characterised by strongly inhomogeneous electron liquids

After a brief summary of some recent work on non-local approximations to the exchange energy and potential in density functional theory, a table is presented for atoms from Be to Ar, with an even number of electrons, having large electron density gradients, which highlights the importance of exchange. Until non-local exchange energy is truly quantitative, refinements of correlation energy may be submerged through ‘noisy’ exchange.