[gmx-users] Entropic effects in PMF at zero distance

[dgfd dgdfg]

The formula  (5.283) from PDF manual or (3) in  http://manual.gromacs.org/documentation/current/reference-manual/special/free-energy-implementation.html#potential-of-mean-force  
V(r)=-(n-1)*kT*log(r)
is obviously incorrect at r=0 for non singular potential (f.e. if "r" is the distance between COMs of two molecules, one of them having cavity at its center). Resulting PMF must be finite at r=0 in contradiction with formula above. Is right variant for the correction of constraint influence for that case exits in literature?