Density-functional theory of the solid-liquid interface

A density-functional theory for the structure and surface free energy {γ} of solid-liquid interfaces is presented which avoids perturbation and square-gradient approximations by the utilization of (i) the weighted-density approximation for the Helmholtz free-energy functional and (ii) a physical, two-parameter density profile of the interfacial region. The hard-sphere [100] fcc-liquid interface is found to be only 4--5 layers wide with {γ}=0.66kT/σ², consistent with simulations on the similar {ε}(r/{σ})^-12 interface.