The fcc (111) and (100) crystal–melt interfaces: A comparison by molecular dynamics simulation

Abstract

The Lennard-Jones fcc (111) and (100) crystal–melt interfaces have been simulated by molecular dynamics with a view to understanding their thermodynamic and structural similarities and/or differences. The atomic and potential energy density profiles look very similar for the two faces, suggesting that any structural and thermodynamic differences are very subtle. Diffusion coefficient data show that the transition from crystal to melt for the (100) face occurs over essentially the same distance as for the (111) face. A careful calculation of excess surface potential energies indicates the (111) interface to be less stable than the (100), but that the energy quantities involved are very small (∼5% of the crystal–vapor values). The excess configurational entropy is negligible in both cases. However, no estimate of the communal entropy has been made, and it could be very important. The Gibbs equimolar dividing surface for the (111) interface coincides with that indicated by the layerwise radial distribution functions and atomic trajectory plots. This is not true of the (100) face; here the dividing surface occurs before the last crystalline layer.