Exploring the energy landscape of PtxAu115−x nanoalloys

Abstract

A detailed structural analysis as a function of chemical composition is performed for the putative global minima of PtxAu115−x clusters. Minimum energy structures were obtained thoroughly exploring the energy landscape through the basin-hopping method, modeling interatomic interaction with the many-body Gupta potential. The structural analysis shows that, over the complete range of compositions, several morphological changes occur as a consequence of Pt doping. Our results show that clusters’ symmetry prevails until a critical composition is reached, where a geometry change arises. The relative stability of Pt–Au clusters as a function of composition is examined through excess energy plot finding that, for a range of compositions, core–shell rhombicosidodecahedral structures are particularly stable under this model potential. For this segregated structure, atomistic centrosymmetry parameter shows the existence of three well-defined shells from which the outermost layer can be interpreted as a surface reconstruction on the 55-atom Pt core that decrease energy and provide higher stability. Mixing energy is minimized at composition Pt55Au60 whose global minimum structure consists of an icosahedral 55-atom platinum core encapsulated by a 60-atom gold shell exhibiting Archimedean polyhedron geometry. The influence of Pt loading is observed trough the menagerie of structural motifs found, the most abundant showing Marks decahedral symmetry. Ab initio DFT calculations show that the truncated octahedron cluster is energetically favored.