Stability of Au–Pd Core–Shell Nanoparticles

Abstract

The stability of Au–Pd alloys with sizes close to 3 nm and icosahedral, decahedral, and truncated octahedral geometries with AucorePdshell and PdcoreAushell elemental distributions have been studied using canonical molecular dynamics simulations. The analysis of excess energy show that the PdcoreAushell ordering is more stable than the AucorePdshell for particles of this size, while the analysis of the order parameter Q6 revealed that some of the particles with AucorePdshell ordering exhibited geometric and structural changes previous to melting of the particles. Analysis of the local density of the species revealed that these changes are due to diffusion of Pd atoms into the inner core of the particles. The geometry and structure of all of the particles with PdcoreAushell were preserved until just before the solid–liquid transition, as well as showing a lower melting temperature than the AucorePdshell particles.