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, $$\Gamma _{{\text{Cu}}}^{\left( {{\text{Ni}}} \right)} $$, of Cu (solute) relative to Ni (solvent) at solid-liquid interfaces in Ni-rich alloys. We derive absorption values of $$\Gamma _{{\text{Cu}}}^{\left( {{\text{Ni}}} \right)} = - 0.05 \pm 0.20$$ and −0.23 ± 0.50 atoms/nm2 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.