Symmetry energies and the curvature of the nuclear mass surface

A global study of the symmetry energies reflects upon the curvature of the mass surface. Special attention is given to the region from Ni-56 to Sn-100. Isospin inversion is indicated for odd-odd self-conjugate nuclei. Coexistence of isoscalar and isovector n-p interactions in the localized region N approximate to Z, A = 76-96 is suggested by the isospin dependence of the symmetry energy. Experimental symmetry energies and values extracted from nine mass equations are compared. Overall agreement exists, but some distinct differences are also observed.