Melting mechanisms of Pt-based multimetallic spherical nanoparticles by molecular dynamics simulation

The melting mechanisms of Pt-based multimetallic nanoparticles (NPs) are important to help determine their optimal melting processes. To understand the melting and coalescence behaviors of heterogeneous NPs (Pd–Pt NPs) with various sizes and compositions, molecular dynamics (MD) simulation was employed. The MD results for larger Pd–Pt NPs with an effective diameter of 4.6–7.8 nm show that PtPd alloy can form at Pd/Pt interface before Pd NP melted completely, while for Pt-core/Pd-shell NP and Pd-core/Pt-shell NP, PtPd alloy formed only after Pd portion melted completely. For smaller Pd–Pt NPs with an effective diameter of 2.5–4.0 nm, PdPt alloy is not formed until both Pd and Pt NPs melted completely. Besides, the coalescence process of Pd–Pt NPs depends on the melting temperature of Pt NP when Pt composition is higher than 20 at%. Furthermore, the melting mechanisms of Pd/Pt/Ir trimetallic NPs are investigated. A two-step melting process occurs in Pd–Pt–Ir NPs and Ir-core/Pt-shell/Pd-shell NP, and the melting sequence of Pd-core/Pt-shell/Ir-shell NP and Pt-core/Pd-shell/Ir-shell NP is different from Pd/Pt bimetallic NPs. Graphical abstract