  Evaporation/condensation transition of the Potts model on square lattice is
numerically investigated by the Wang-Landau sampling method. Intrinsically
system size dependent discrete transition between supersaturation state and
phase-separation state is observed in the microcanonical ensemble by changing
constrained internal energy. We calculate the microcanonical temperature, as a
derivative of microcanonical entropy, and condensation ratio, and perform a
finite size scaling of them to indicate clear tendency of numerical data to
converge to the infinite size limit predicted by phenomenological theory for
the isotherm lattice gas model.
