  The nuclear binding energies for 28 nuclei including several isotopic chains
with masses ranging from A=64 to A=226 were evaluated using the Skyrme
effective nucleon-nucleon interaction and the Extended Thomas-Fermi
approximation. The neutron and proton density distributions are assumed in the
form of Fermi functions the parameters of which are determined so as to
minimize the total binding energy of any given nucleus. The present study is
restricted to quadrupole shapes, but the neutron and proton density
distributions are free to have different deformations. A simple expression for
the variation of the nuclear energy with the neutron--proton deformation
difference is derived.
