  A spatial distribution of electric charges forming a square potential well
has been studied. It is shown that this potential is created by two spherical
double charge layers, which is in contradiction with a real molecular structure
of C60 cage. A C60 shell potential has been calculated in the assumption that
it is formed by the averaged charge density of a neutral atom. It is shown that
the phenomenological potentials simulating the C60 shell potential should be
selected from a family of potentials with a none-flat bottom. Two possible
types of C60 model potentials have been considered and their parameters have
been calculated.
