The threshold method is used to explore the potential energy surface of the Pt(1)Pd(12) bimetallic cluster, defined by the Gupta semiempirical potential. A set of helical structures, which follow a Bernal tetrahelix pattern, correspond to local minima for the Pt(1)Pd(12) cluster, characterizing the region of the energy landscape where these structures are present. Both right-handed and left-handed chiral forms were discovered in our searches. Energetic and structural details of each of the tetrahelices are reported as well as the corresponding transition probabilities between these structures and with respect to the icosahedron-shaped global minimum structure via a disconnectivity graph analysis.

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The evolution of the structure of bimetallic Pt101–x Au 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.

In this work we present a thorough exploration of the potential energy surface (PES) of Pd-Pt bimetallic nanoparticles at the specific composition Pd 12 Pt 1 , using the combination of a genetic algorithm and the threshold method for global optimization and exploration of the barrier structure, employing the semiempirical Gupta many-body potential for modeling the interatomic interactions. The structural and energetic analysis of Pd 12 Pt 1 nanoparticles, including binding energies (E b ), symmetries and commonneighbor analysis (CNA) allowed us to identify a large set of representative structures of local minima, with an icosahedral motif found to be the putative global minimum for Pd 12 Pt 1 . A detailed study of the icosahedral motif was carried out by an exhaustive exploration of low energy isomers, in order to understand qualitatively structural interconversion. 2-D tree (disconnectivity) graphs are plotted to map the structures of minima on the PES of Pd 12 Pt 1 . DFT calculations were performed on representative structures to establish the energetic hierarchy and structural stability. 5-088,

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