NUMERICAL RESULTS FOR GENERALIZED RESONATING-VALENCE-BOND WAVE-FUNCTIONS - APPLICATION TO THE HUBBARD-MODEL

Numerical results are presented for a generalized resonance-valence-bo nd state which includes both ionic and covalent contributions in each bond; non-nearest-neighbor bonds are also considered. Variational calc ulations have been performed and the space-group symmetry has been tak en into account. The results for the Hubbard Hamiltonian are compared with the exact ones for the 2 x 2 x 2 and the 4 x 4 lattices. The agre ement is quite satisfactory for large values of the interaction U (for U = 40; the overlap with the exact ground-state wave function is 0.99 9). Several correlation functions are also compared.