Surface segregation and mixing propensity in noble metal AgAuCuPdPt nanoalloys upon element enrichment - A computational perspective

Abstract

High-entropy Ag-Au-Cu-Pd-Pt nanoparticles in the 2400--6300-atom size range were computationally studied at thermodynamical equilibrium and room temperature using a combination of well established many-body potentials and Monte Carlo methods. Tools from percolation theory are used to further quantify the deviations to ideal behavior from noninteracting solid solutions. Upon varying the concentration of each element one at a time, the possible surface enrichment in the various metals is determined and the fragment statistics provide insight into the spatial distribution of atoms within the nanoparticles and their tendency for mixing or segregation. The effects of size and dimensionality are addressed separately, by comparing the results obtained for the 0D (nanoparticle) system with those for the 2D (slabs) and 3D (periodic) samples. Although these properties are found to depend on the underlying many-body potential to some extent, some robust trends are predicted notably for silver and platinum, which strongly segregate and preferentially reside at the surface and in the core of the nanoparticles, respectively.