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.

We present a systematic study of the structural changes of 19-atom Pd n Pt 19-n nanoparticles as a function of composition, modeling the interatomic interactions with the many-body Gupta potential and using a genetic algorithm to obtain the lowest energy structures for all possible compositions. Topological analysis reveals that most of the structures are based on icosahedral packings and are strongly composition dependent. The pure Pd 19 nanoparticle exhibits a double icosahedral geometry, while the Ino decahedron is the basis of the Pt 19 cluster structure, which has a lower symmetry. Several structural motifs of the predicted lowest energy configurations are observed for bimetallic clusters in the range of compositions studied here. Six ideal structural families have been identified. Our results show that, for Pt-rich clusters, Pt atoms segregate into the core and the number of Pd-Pt bonds increases, while for Pd-rich clusters, the surface-segregated Pd atoms tend not to be nearest-neighbors. X-ray diffraction structure factors are simulated for all the predicted structures.

In this work, we report finding dodecahedral core-shell structures as the putative global minima of Pt13M20 (M = Ag, Au, Cu, Pd) clusters by using the basin hopping method and the many-body Gupta model potential to model interatomic interactions. These nanoparticles consist of an icosahedral 13-atom platinum core encapsulated by a 20 metal-atom shell exhibiting a dodecahedral geometry (and Ih symmetry). The interaction between the icosahedral platinum core and the dodecahedral shell is analyzed in terms of the increase in volume of the icosahedral core, and the strength and stickiness of M-Pt and M-M interactions. Low-lying metastable isomers are also obtained. Local relaxations at the DFT level are performed to verify the energetic ordering and stability of the structures predicted by the Gupta potential finding that dodecahedral core-shell structures are indeed the putative global minima for Pt13Ag20 and Pt13Pd20, whereas decahedral structures are obtained as the minimum energy configurations for Pt13Au20 and Pt13Cu20 clusters.

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