ACCURATE NUMERICAL DETERMINATION OF KOHN-SHAM-POTENTIALS FROM ELECTRONIC DENSITIES .1. 2-ELECTRON SYSTEMS

The extraction of the true Kohn-Sham exchange-correlation potential fr om near-exact electronic densities is demonstrated, with particular re ference to the two-electron systems He and HZ It is shown that if the reference density is obtained from a standard configuration interactio n calculation, very large orbital basis sets are required to obtain co nvergence in the resulting exchange-correlation potential. The correla tion contribution to molecular bonding is analysed in terms of contrib utions from the potential in different regions of real space. (C) 1997 American Institute of Physics.