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/${\mathrm{\sigma }}^2$, consistent with simulations on the similar ε(r/σ${)}^{\mathrm{-}12}$ interface.