  The critical radius of a nucleus grown by diffusion in a solution is studied
thermodynamically as well as kinetically. The thermodynamic growth equation
called Zeldovich equation of classical nucleation theory (CNT) and the kinetic
diffusional growth equation combined with the Ostwald-Freundlich boundary
condition lead to the same critical radius. However, it should be pointed out
that the diffusional equation may lead to a kinetic critical radius that is
different from the thermodynamic critical radius, thus indicating the
possibility of kinetically controlling the critical radius of a nucleus.
