Structural motifs of bimetallic Pt_{101- x}Au_x nanoclusters

The evolution of the structure of bimetallic Pt_101-xAu _x (x = 0-101) clusters is theoretically studied as a function of composition. The basin hopping method using the Gupta empirical potential (EP) is used to perform an exhaustive sampling of the potential energy surface (PES). Several highly symmetric morphologies such as Marks decahedra, incomplete icosahedra, two types of anti-Mackay-covered 5-fold structures, Leary tetrahedra and close-packed structures are identified and reoptimized at the first-principles density functional theory (DFT) level to take into account electronic effects. Alloyed configurations at very low Pt content and ubiquitous Pt(core)Au(shell) segregated motifs with different morphology and core shape are found as the lowest energy structural motifs at the empirical potential level, with an appreciable influence of Pt concentration on the nanocluster structure and a strong competition between different structural motifs, especially in the region of the lowest values of mixing energy. At variance with these predictions, at the DFT level a core-shell crystalline motif (which is only marginally present as a global minimum at the Gupta level) becomes dominant over a broad range of compositions including pure particles. This shows the importance of adopting a combined DFT/empirical-potential investigation for third-row transition metal clusters, also in connection with the prediction of the catalytic properties of these systems.