Variational calculation of many-body wave functions and energies from density functional theory

A generating coordinate is introduced into the exchange-correlation functional of density functional theory (DFT). The many-body wave function is represented as a superposition of Kohn-Sham (KS) Slater determinants arising from different values of the generating coordinate. This superposition is used to variationally calculate many-body energies and wave functions from solutions of the KS equation of DFT. The method works for ground and excited states, and does not depend on identifying the KS orbitals and energies with physical ones. Numerical application to the Helium isoelectronic series illustrates the method's viability and potential. (C) 2003 American Institute of Physics.