During several short visits to the Max-Plank Institute für Festkoperforschung (Stuttgart) in 1991 and 1992, I have been applying the ab initio Local Ansatz method (developed by G.Stollhoff and P.Fulde) to study correlation effects in AgCl. We have found (unpublished) that a smaller lattice constant in the crystal, in comparison with our HF calculations using CRYSTAL code, originates predominantly from intra-correlation effects within silver ions.