First-principles-based study on phase stability of Cu-Pt-Rh disordered alloys

摘要

Very recently, the authors predict through DFT-based investigation that Pt-Rh and Pt-Cu alloys can be potential candidate for the anode catalyst of the polymer-electrolyte fuel cells (PEFC). At T=0 K, these alloy surfaces both consist mainly of Pt atom at the topmost layer owing to strong Pt segregation to the surface, while the second layer consists mainly of Rh or Ca atoms. The theoretical investigation elucidated that the catalytic property of Pt atoms at the topmost layer significantly changes with atomic arrangements or composition at the second layer because of the chemical effect between top and the second layers. These facts naturally suggest the possibility of Cu-Pt-Rh ternary alloy to be potential candidate for the PEFC catalyst. Despite such interests, phase stability of the Cu-Pt-Rh alloy in both bulk and surface has not been investigated so far. In the present study, we investigate phase equilibria of disordered Cu-Pt-Rh alloy based on combination of cluster expansion (CE) technique and first-principles calculation. The effects of a finite temperature on atomic arrangements can be included using Monte Carlo (MC) simulation under canonical ensemble with effective cluster interactions (ECIs) obtained through the CE.