For *N* > 4, the dependence *U*_{Ne}(*r*) has a
maximum at *r*
0 and a
minimum at *r* = 0 which corresponds to merging of the two particles.

For *N* = 4, the dependence *U*_{Ne}(*r*) is given
by a monotonically decreasing function exhibiting no extrema.

For *N* = 2 and *N* = 3, the function
*U*_{Ne}(*r*) has a minimum at *r*
0 and
*r*
.

For *N* = 1, the function *U*_{Ne}(*r*) is
monotonically increasing.