The binding energy of atoms interacting via pairwise Morse potentials is calculated by several methods for large clusters of face-centered cubic (fcc) and icosahedral structures: by numerical calculations for bulk particles, by direct numerical calculations for numbers of atoms n =561-923, and by analytical methods using perturbation theory. A phase diagram is constructed for a wide range of cluster sizes, which links the adjustable range parameter of the Morse potential to the cluster energy along the curve corresponding to the set of conditions for which the energies of the fcc and icosahedral structures are equal.