Atomic-scale simulation study of equilibrium solute adsorption at alloy solid-liquid interfaces

Equilibrium structural properties of solid-liquid interfaces in Cu-Ni alloys are studied by Monte-Carlo simulations employing interatomic potentials based on the embedded-atom method. We describe a thermodynamic-integration approach used to derive bulk concentrations and densities for solid and liquid phases in two-phase thermodynamic equilibrium. These results are used as a basis for constructing three-dimensional supercell geometries employed in Monte-Carlo-simulation studies of solid-liquid interface properties for {100} and {111} crystallographic orientations. At a temperature of 1750 K (four percent below the calculated melting point of pure Ni) equilibrium density and concentration profiles have been derived, allowing a calculation of the relative Gibbsian adsorption, Gamma(Cu)(( Ni)), of Cu (solute) relative to Ni (solvent) at solid-liquid interfaces in Ni-rich alloys. We derive absorption values of Gamma(Cu)(( Ni))= -0.05+/- 0.20 and -0.23 +/- 0.50 atoms/nm(2) for {100} and {111} interfaces, respectively. These results are discussed in the context of available experimental measurements and continuum-theory results for adsorption at heterophase interfaces.