Competition between structural motifs in gold–platinum nanoalloys

The structures of AuPt nanoalloys of size 55 atoms are computationally studied by a procedure combining global optimization searches within an atomistic potential model with density-functional theory (DFT) relaxation of the lowest-energy isomers. The study focuses mainly on the intermediate composition range, in which two structural motifs are found to be in close competition: the Mackay icosahedron and an asymmetric capped decahedron. Other structural motifs, such as the Ino decahedron and the cuboctahedron are found to be much higher in energy. Our results show that there is a window of compositions in which the asymmetric capped decahedron is the most stable of these motifs. The comparison of atomistic and DFT results shows that the potential is quite accurate for intermediate compositions, whereas clear discrepancies are found on the Pt-rich side.