Simulation of size effects upon phase transformations in submicrometer particles of an Au–Pt–Pd alloy

Size effects act at phase equilibria in micro- and nanoparticles They appear as shifts of the characteristic lines and points in the phase diagrams. We simulated and visualized these effects in ternary systems, such as Au-Pt-Pd solid solution. We applied methods of chemical thermodynamics to study the influence of the alloy composition on the region where core-shell states for the particles with a radius of 250 nm exist. It was shown that the splitting area of the alloy decreases and splits due to competing core-shell states, with Pt segregation in either core or shell phase. The phase diagram contains nodes of stable and metastable core-shell equilibrium states. We studied some of the properties of these states (composition of coexisting solutions, radius of the core phase). The described effects are relevant for understanding the catalytic activity of Au-Pt-Pd alloy particles.