The anisotropic free energy of the Lennard-Jones crystal-melt interface

We have calculated the free energy of the crystal-melt interface for the Lennard-Jones system as a function of crystal orientation, near zero pressure, by examining the roughness of the interface using molecular dynamic simulations. The anisotropy is weak, but can be accurately resolved using this approach due to the sensitivity of the fluctuations on the anisotropy. We find that the anisotropy can be described well using two parameters, based upon a low-order expansion satisfying cubic symmetry. The results are in good agreement with previous calculations of the free energies, based upon simulations used to calculate the reversible work required to create the interfaces. The weak anisotropy is also in reasonable agreement: The work here and the work of Davidchack and Laird [R. L. Davidchack and B. B. Laird, J. Chem. Phys. 118, 7651 (2003)] both predict gamma(100)>gamma(110)>gamma(111). The only discrepancy is that we find a smaller value for the difference gamma(100)-gamma(111) by an amount larger than the combined error bars. (C) 2003 American Institute of Physics.