Configurational thermodynamics of alloyed nanoparticles: a first-principles cluster expansion study

Transition-metal, alloyed core-shell nanoparticles (NPs) continue to be studied as heterogeneous catalysts because they are found to improve catalytic activity and selectivity for many energy-conversion processes. However, thermodynamic investigations have been limited mostly to NP core-shell preference, rather than both geometric structure and its chemical decoration. Here, by extending cluster expansion methods to treat alloyed nanoparticles, we study the configurational thermodynamics of bimetallic NPs, using databases from density functional theory calculations. We find that the interplay between the ordering tendency and the core-shell segregation tendency can induce site-specific preferences around the NP, as we exemplify, e.g., in AgAu. Such simulations will provide information needed for further understanding of the structure-function relationships in NP catalysis.