  Systematic calculations of the Coulomb barrier parameters for collisions of
spherical nuclei are performed within the framework of the double folding
approach. The value of the parameter $B_Z=Z_PZ_T/(A^{1/3}_P+(A^{1/3}_P)$ (which
estimates the Coulomb barrier height) varies in these calculations from 10 MeV
up to 150 MeV. The nuclear densities came from the Hartree-Fock calculations
which reproduce the experimental charge densities with good accuracy. For the
nucleon-nucleon effective interaction two analytical approximations known in
the literature are used: the M3Y and Migdal forces. The calculations show that
Migdal interaction always results in the higher Coulomb barrier. Moreover, as
$B_Z$ increases the difference between the M3Y and Migdal barrier heights
systematically increases as well. As the result, the above barrier fusion cross
sections calculated dynamically with the M3Y forces and surface friction are in
agreement with the data. The cross sections calculated with the Migdal forces
are always below the experimental data even without accounting for the
dissipation.
