Monte Carlo test of the classical theory for heterogeneous nucleation barriers.

Flat walls facilitate the condensation of a supersaturated vapor: classical theory of heterogeneous nucleation predicts that the free energy barrier DeltaF(het)*, which needs to be overcome for the formation of sphere-cap-shaped nucleation seeds, is smaller than the barrier DeltaF(hom)* for spherical droplets in the bulk by a factor 0 < f(theta) < 1, which only depends on the contact angle theta. In this Letter, we compute both DeltaF(hom)* and DeltaF(het)* from Monte Carlo simulations and test the theory for the lattice gas model (for which theta can be readily controlled). Even though the theory is only based on macroscopic arguments, it is shown to hold for experimentally relevant nanoscopic nucleation seeds (20 < or = DeltaF(hom)*/k(B)T < or = 200) if (independently estimated) line tension effects are considered.