  In this work we have studied a new functional for the correlation energy
obtained from the exact-exchange (EXX) approximation within time-dependent
density functional theory (TDDFT). Correlation energies have been calculated
for a number of different atoms showing excellent agreement with results from
more sophisticated methods. These results loose little accuracy by
approximating the EXX kernel by its static value, a procedure which enormously
simplifies the calculations. The correlation potential, obtained by taking the
functional derivative with respect to the density, turns out to be remarkably
accurate for all atoms studied. This potential has been used to calculate
ionization potentials, static polarizabilities and van der Waals coefficients
with results in close agreement with experiment.
