NEW FUNCTIONALS FOR CORRELATION-ENERGY DEDUCED IN THE FRAMEWORK OF THE CORRELATION FACTOR APPROACH

The general characteristics of two-body density functionals (TBDF) are explored and two new correlation energy functionals are derived using the correlation factor approach. The optimization of the parameters e ntering the above functionals requires exact and accurate atomic corre lation energies (ACE). We revised the ACE values in the literature and obtained a new set of ''exact'' ACE for atoms with 2 less than or equ al to Z less than or equal to 10. Unfortunately, there exist some inac curacies in the ACE values of the second-row atoms, which make unsuita ble the inclusion of them in the optimization. The ACE calculated for the first period with the above functionals, using the optimized sets of parameters, are in excellent agreement with the exact ones, while t he corresponding values calculated for the second-row atoms are betwee n the precision margins estimated by us for the exact values. (C) 1997 John Wiley & Sons, Inc.