In this contribution, a recently proposed parameterisation scheme for the Modified Embedded Atom Method (MEAM), is presented. This new approach is entirely based on ab initio DFT data, including not only bulk material properties, but also surface effects. Based on this approach, new MEAM parameters are determined for Cu, Pt, Pd and Rh and all their binary alloys. Next, the MEAM is used in Monte Carlo simulations for the prediction of the surface segregation and ordering as a function of temperature in binary alloys with different types of ordering tendencies.
Pt-Rh and Pt-Pd form disordered solid solutions at all temperatures. The simulation results for the segregation to Pt25Rh75 and Pt50Rh50 low index and vicinal surfaces show good agreement with the experiments, including the formation of a (2x1) missing-row reconstruction on Pt25Rh75(110). Also for Pt-Pd, the results are in good agreement with other experimental and theoretical work.
Pd-Rh and Cu-Rh feature a phase separating tendency at lower temperatures, which is indeed reproduced by our MC/MEAM simulations, in good agreement with the experimental phase diagram. The MC/MEAM simulations for the surface slabs predict a cherry-like configuration with the phase of lower surface energy located in the surface region, while the coexisting phase of higher surface energy constitutes the center of the film. An important difference between these two systems is the nature of the composition depth profile: in Pd-Rh alloys, the Pd enrichment decreases monotonically, while in Cu-Rh alloys, the composition oscillates slightly. This result is validated with approximative calculations of the layer-dependent segregation energy, both by DFT and the MEAM.
Finally, Cu-Pt and Cu-Pd form ordered compounds at lower temperatures. Segregation to Cu3Pt and Cu3Pd low index surfaces are simulated as a function of temperature. The simulations are overall in good agreement with the experimental data, except for Cu3Pt(110). This discrepancy is further investigated by calculating the surface energy for the two possible trunctations, both by DFT and the MEAM. Also for Cu3Pd, the results are rationalised by DFT calculations for different bulk truncations.
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