  Using the structural data of the La2CuO4 compound both in the low temperature
tetragonal phase and in the isotropic phase we have derived an effective t-J
model with hoppings t and superexchange interactions J extended up to fourth
and second neareast neighbors respectively. By numerically studying this
hamiltonian we have then reproduced the main experimental features of this HTc
compound: d-wave superconductivity is stabilized at small but finite doping
delta>6% away from the antiferromagnetic region and some evidence of dynamical
stripes is found at commensurate filling 1/8.
