Embedded cluster calculation for the Hubbard model

The fermion cluster approximation by Caron and Pratt in the corrected form given in a previous paper is applied to the two-site Hubbard model. Because the approximation in its standard form is unable to describe energy bands the boundary condition integration technique of C. Gros for free clusters generalized to embedded clusters has been used to average over the solutions to different self-consistency equations. As an example the Mott-Hubbard transition was determined. ((orig.))