Kinetics of chemical ordering in a Ag-Pt nanoalloy particle via first-principles simulations

• Published in: The Journal of chemical physics 2012-11, Vol.137 (19), p.194302-194302
• Main Authors: Negreiros, F R, Taherkhani, F, Parsafar, G, Caro, A, Fortunelli, A
• Format: Article
• Language: English
• Subjects: Alloying; Barriers; Clusters; DENSITY FUNCTIONAL METHOD; Energy use; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; KINETIC ENERGY; KINETICS; MATERIALS SCIENCE; Nanostructure; NANOSTRUCTURES; Nuclear power generation; PHASE DIAGRAMS; Platinum; PLATINUM ALLOYS; Silver; SILVER ALLOYS; SIMULATION; VACANCIES
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.4759507

The energetics and kinetic energy barriers of vacancy/atom exchange in a 37-atom truncated octahedron Ag-Pt binary cluster in the Ag-rich range of compositions are investigated via a first-principles atomistic approach. The energy of the local minima obtained considering various distributions of a single vacancy and a few Pt atoms within the cluster and the energy barriers connecting them are evaluated using accurate density-functional calculations. The effects of the simultaneous presence of a vacancy and Pt atoms are found to be simply additive when their distances are larger than first-neighbors, whereas when they can be stabilizing at low Pt content due to the release of strain by the Pt/vacancy interaction or destabilizing close to a perfect Pt(core)/Ag(shell) arrangement. It is found that alloying with Pt appreciably increases the barriers for homotops transformations, thus rationalizing the issues encountered at the experimental level in producing Ag-Pt equilibrated nanoparticles and bulk phase diagram.