FINITE-SIZE EFFECTS ON THE APPROACH OF COMPLETE WETTING

We perform an exact model calculation of the unbinding transition of a one-dimensional interface from a substrate on the approach of two-pha se coexistence. This transition is modelled in a solid-on-solid (sos) model with discrete columns which have a partition function calculated for a finite substrate area A. In the limits of large A and a small d istance \Delta mu\ to coexistence, the partition function becomes a fu nction of the the scaling variable x = \Delta mu\(2/3) A. The interfac e-to-substrate distance l diverges as l alpha \Delta mu\(-beta), with beta = -1/3 if the two limits are taken at constant or diverging x. If x vanishes, a finite-size regime appears in which beta = -1. A relate d interface model in continuous space was studied earlier by Kroll and Gompper and our scaling functions are identical to theirs.