Molecular dynamics investigation of the crystal-fluid interface. IV. Free energies.

The excess free energy, entropy and energy have been obtained for crystal-vapor interfaces by molecular dynamics. The face centered cubic (111), (100) and (110) faces of a crystal composed of Lennard Jones particles were investigated. At low temperatures the free energies of the three faces are ordered as expected, in accord with the density of atoms in the layers. But within 20% of the triple point the free energy is nearly isotropic. The surface stress remains highly anisotropic at all temperatures. Comparisons are made with analogous quantities obtained for the liquid-vapor system near the triple point.