EXACT EXCHANGE KERNEL FOR TIME-DEPENDENT DENSITY-FUNCTIONAL THEORY

An exact expression for the exchange kernel of time-dependent density- functional theory, the frequency-dependent functional derivative of th e exchange potential with respect to the density, is derived. The expr ession is simple enough to be applied in practice. A simple and transp arent derivation of the coupled Kohn-Sham equation of time-dependent d ensity-functional theory is given. Modified coupled Kohn-Sham equation s are presented that are especially well suited for an ''exact-exchang e'' treatment of excitation energies, polarizabilities, and other line ar response properties. (C) 1998 John Wiley & Sons, Inc.