Atomistic simulations of fee Pt ₇₅Ni ₂₅ and Pt ₇₅Re ₂₅ cubo-octahedral nanoparticles

We have developed interatomic potentials for Pt-Ni and Pt-Re alloys within the modified embedded atom method (MEAM). Furthermore, we applied these potentials to study the equilibrium structures of Pt ₇₅Ni ₂₅ and Pt ₇₅Re ₂₅ nanoparticles at T=600 K using the Monte Carlo method. In this work, the nanoparticles are assumed to have disordered fcc cubo-octahedral shapes (terminated by {111} and {100} facets) and contain from 586 to 4033 atoms (corresponding to a diameter from 2.5 to 5 nm). It was found that, due to surface segregation, (1) the Pt ₇₅Ni ₂₅ nanoparticles form a surface-sandwich structure: The Pt atoms are enriched in the outermost and third atomic shells, while the Ni atoms are enriched in the second atomic shell; (2) the equilibrium Pt ₇₅Re ₂₅ nanoparticles adopt a core-shell structure: A Pt-enriched shell surrounding a Pt-deficient core.