  We consider the extension of the standard single-determinant Kohn-Sham method
to the case of a multiconfiguration trial wavefunction. By applying the
rigorous Kohn-Sham method to this case, we construct the proper interacting and
non-interacting energy functionals. Following the Hohenberg-Kohn theorem for
both energy functionals, we derive the corre-sponding multiconfiguration
Kohn-Sham equations. At the end of the analysis we show that, at the ground
state, the multiconfiguration wavefunction must collapse into a
single-determinant wavefunction, equal to the regular KS wavefunction. We also
discuss the non-collapse of the wavefunction in other multiconfiguration
density functional theory methods where the auxiliary system is partially
interacting.
