Insight into the Melting Behavior of Au–Pt Core–Shell Nanoparticles from Atomistic Simulations

Comprehensive understanding of thermodynamic properties of metallic nanoparticles is of significance for their utility in catalysis. In this article, we have employed molecular dynamics simulations with quantum Sutton–Chen many-body potentials to examine the thermal stability of Au–Pt core–shell nanoparticles with different sizes during continuous heating. Our study shows that, for fixed particle size, the melting temperature is independent of core size for a small core while it is linearly decreased with a rising core radius for a large core. Diverse melting mechanisms have been discovered for different-core-sized nanoparticles. For a small core, the melting is progressively developed from the surface into the core, similar to that of monometallic nanoparticles. For a moderate or large core, an inhomogeneous melting has been found in these nanoparticles. The nucleation and activity of Shockley partial dislocations have initialized the local structural instability of the core–shell interface, leading to the inhomogeneous premelting of the Au core and the Pt shell for the moderate core. Nevertheless, when the core is large enough (resulting superthin shell), the diffusion of Au atoms from the core into the shell plays a dominant role in the destruction of the core–shell interface. This study provides a fundamental perspective on the melting behaviors of bimetallic (even multimetallic) nanoparticles at the atomistic level.