Irreducible Finite-Size Effects in the Surface Free Energy of NaCl Crystals from Crystal-Nucleation Data

In this Letter we report a simulation study in which we compare the solid-liquid interfacial free energy of NaCl at coexistence, γ_LS, with the value that follows from the height of the homogeneous nucleation barrier. The two estimates differ by more than 100%. Smaller discrepancies are found for γ_LS of hard-sphere and of Lennard-Jones particles. We consider a variety of possible causes for this discrepancy and conclude that it is due to a finite-size effect that cannot be corrected for by any simple thermodynamic procedure. By taking into account the finite-size effects of γ_LS obtained in real nucleation experiments, we obtain quantitative agreement between γ_LS estimated in the simulations and derived from the experiments. Our finding suggests that most published solid-liquid surface free energies derived from nucleation experiments will have to be revised.