The expansion of the nucleation free energy barrier as a power series in Dμ (the excess chemical potential) is examined using density functional theory. For attractive intermolecular potentials decreasing with separation, r, more rapidly than r-6 a power series expansion of the form is possible. The parameters B, C and D can be related to properties of the planar interface and resulting values give a satisfactory estimate of the barrier height. However, ignoring the term, , as proposed by some authors, leads to poorer agreement and incorrect estimates of the parameter D.
