TY - DATA T1 - Gold–Copper Nano-Alloy, “Tumbaga”, in the Era of Nano: Phase Diagram and Segregation PY - 2015/12/17 AU - Grégory Guisbiers AU - Sergio Mejia-Rosales AU - Subarna Khanal AU - Francisco Ruiz-Zepeda AU - Robert L. Whetten AU - Miguel José-Yacaman UR - https://acs.figshare.com/articles/media/Gold_Copper_Nano_Alloy_i_Tumbaga_i_in_the_Era_of_Nano_Phase_Diagram_and_Segregation/2043831 DO - 10.1021/nl503584q.s004 L4 - https://ndownloader.figshare.com/files/3615147 KW - icosahedron KW - surface KW - nanophase diagrams KW - sizes 4 KW - rhombic dodecahedron KW - phase diagrams KW - Phase Diagram KW - core KW - polyhedral nanoparticles KW - octahedron KW - copper enrichment KW - gold enrichment KW - 10 nm KW - EDX KW - phase diagram N2 - Gold–copper (Au–Cu) phases were employed already by pre-Columbian civilizations, essentially in decorative arts, whereas nowadays, they emerge in nanotechnology as an important catalyst. The knowledge of the phase diagram is critical to understanding the performance of a material. However, experimental determination of nanophase diagrams is rare because calorimetry remains quite challenging at the nanoscale; theoretical investigations, therefore, are welcomed. Using nanothermodynamics, this paper presents the phase diagrams of various polyhedral nanoparticles (tetrahedron, cube, octahedron, decahedron, dodecahedron, rhombic dodecahedron, truncated octahedron, cuboctahedron, and icosahedron) at sizes 4 and 10 nm. One finds, for all the shapes investigated, that the congruent melting point of these nanoparticles is shifted with respect to both size and composition (copper enrichment). Segregation reveals a gold enrichment at the surface, leading to a kind of core–shell structure, reminiscent of the historical artifacts. Finally, the most stable structures were determined to be the dodecahedron, truncated octahedron, and icosahedron with a Cu-rich core/Au-rich surface. The results of the thermodynamic approach are compared and supported by molecular-dynamics simulations and by electron-microscopy (EDX) observations. ER -