Liquid–vapor interface in the Li–Na liquid alloy. An ab initio molecular dynamics study

We report the results of an ab initio molecular dynamics simulation of the liquid–vapor interface of the Li–Na liquid alloy at three different concentrations. The study has been performed using samples of 2000 particles in a slab geometry with periodic boundary conditions. The partial longitudinal ionic density profiles for the Li and Na ions along the normal interfaces, clearly reflect the segregating tendencies exhibited by the bulk alloy. Furthermore, the prospective tendency to migrate towards the surface by the ions of the component with the lower surface tension, is now strongly enhanced, giving rise to an interface that is entirely composed by an approximately 2.5 Å wide monolayer of Na ions. The total longitudinal ionic density profile shows a rather weak stratification that extends for three layers into the bulk liquid.