We have developed ReaxFF force fields for Fe-Ni-Al alloys. The ReaxFF force field parameterswere optimized for the Fe-Ni, Fe-Al and Ni-Al interactions of the binary alloys based on the abinitio calculations using projector augmented wave (PAW) potential as implemented in theVASP. A series of DFT calculations for energy and structure were performed on bulk Fe-X (X=Ni, Al) binary alloys with X concentrations up to 75 at. %. Along with bulk systems analysis,Fe-Al and Ni-Al surface events, e.g., adsorption and substitution on vacancy were alsoinvestigated for the training of the ReaxFF potentials.The chemical composition and the relative stability of the ordered alloy surface wereinvestigated by annealing the binary alloy clusters at high temperature using molecular dynamicssimulations. The ratio of metal atoms (Fe:Ni, Fe:Al and Ni:Al) was calculated by analyzing thenumber distributions from the bulk to the topmost surface layer. The ratio shows that afterannealing, Ni- or Al-segregation occurs near the surface region, consequently inducing the Ni- orAl-depletion region next to the Ni and Al-enriched surface layers. These simulation results arein good qualitative agreement with the surface segregation phenomena observed in experiment.The ReaxFF force field simulations were able to predict surface segregation profiles across thelayers of the alloy cluster, thus providing the fundamentals to an ongoing study of the complexsurface oxidation processes in alloys.

Development of ReaxFF reactive force field for Fe-Al-Ni alloy and the study of surface segregation

243rd National Meeting (2012)

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