G. Fano et al., NUMERICAL RESULTS FOR GENERALIZED RESONATING-VALENCE-BOND WAVE-FUNCTIONS - APPLICATION TO THE HUBBARD-MODEL, Physical review. B, Condensed matter, 54(24), 1996, pp. 17557-17563
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.