Direct Calculation of the Hard-Sphere Crystal /Melt Interfacial Free Energy

We present a direct calculation by molecular-dynamics computer simulation of the crystal/melt interfacial free energy γ for a system of hard spheres of diameter σ. The calculation is performed by thermodynamic integration along a reversible path defined by cleaving, using specially constructed movable hard-sphere walls, separate bulk crystal, and fluid systems, which are then merged to form an interface. We find the interfacial free energy to be slightly anisotropic with γ = 0.62±0.01, 0.64±0.01, and 0.58±0.01k_BT/σ² for the (100), (110), and (111) fcc crystal/fluid interfaces, respectively. These values are consistent with earlier density functional calculations and recent experiments.