Structure and dynamics of 38-atom Ag-Pt nanoalloys using ANN based-interatomic potential

Abstract

Silver–platinum nanoalloys are potential candidates as effective and less expensive catalysts than pure platinum-based catalysts. The reactivity of these nanoalloys depends crucially on their size, composition, and ordering of the constituent Ag and Pt atoms. Moreover, the presence of a second metal atom in these nanoalloys results in a variety of structural configurations in comparison to their pure counterparts. To explore the structural aspects further, in this paper, we developed an interatomic potential for Ag–Pt nanoalloys based on an artificial neural network model. We systematically carried out structural and energetic analysis of Ag38−nPtn (n = 1 −8) nanoalloys. Using neural network-based interatomic potential, we have also performed molecular dynamics simulations and global optimizations to search the global minimum structures as well as to investigate the effect of temperature on the structures of silver–platinum nanoalloys. We find the lowest energy isomers of Ag38−nPtn nanoalloys are a core–shell structure in which the Pt atoms occupy the core region while the Ag atoms are located in the surface region. The relative stability of nanoalloys has been investigated using excess energy and second-order energy difference calculations. The charge distribution over Pt and Ag atoms is determined for all the lowest energy isomers of Ag38−nPtn nanoalloys. Furthermore, the probability of the presence of a Pt atom on the surface sites in Ag38−nPtn nanoalloys has been calculated at finite temperatures. We find that at 360K, at least one Pt atom moves from the core to the surface region of the Ag38−nPtn nanoalloys.