The Hubbard Hamiltonian reduces the electron interactions in extended systems to a short-range repulsion U ≥ 0 on a lattice of single orbital sites. The nearest-neighbour sites are connected by hopping matrix elements t. Therefore, the physics of the model is governed by the correlation strength U/t. In the case of U t, the energy penalty U for a double occupancy of sites outweighs the kinetic energy gain t and the system becomes strongly correlated. In this limit, the performance of various many-body methods has been tested. These include exact diagonalization schemes such as the Lanczos algorithm , as well as approximate many-body methods such as the random phase approximation (RPA) , truncated CC methods , dynamical mean-field theory (DMFT) and Quantum Monte Carlo (QMC) methods . To evaluate the performance of correlated many-body methods, the one-dimensional half-filled model is especially instructive, as it can be solved exactly. This solution shows that the one-dimensional half-filled Hubbard model is insulating in the strongly correlated limit. In the following, we therefore examine the one-dimensional spinless periodic six-site Hubbard model at half-filling.