Research of surface diffusion and growth of Ni-Pd nanoparticles

Building upon the foundation of embedded atom method potential, this study employs the Nudged Elastic Band method to computationally investigate the diffusion and structural behaviour of Ni-Pd bimetallic nanoparticles on Wulff surfaces. The results reveal that, whether Ni or Pd serves as the substrate, the energy barrier is significantly lower when adatom exchange occurs with two adjacent (111) interfacet atoms compared to the interfacet of (111) and (100). The optimal diffusion path is identified as the centre-positive diagonal exchange (CPDE). Furthermore, it is observed that the energy of the system decreases after the exchange diffusion with the substrate surface atoms. However, successful exchange diffusion requires overcoming specific energy barriers (>0.43 eV), enabling the deposition of NicorePdshell and PdcoreNishell nanoparticles at low temperatures. In Ni-Pd nanoparticles, surface energy plays a predominant role when the size is very small (Natom≦55), leading to the stable configuration of NicorePdshell nanoclusters. However, as the size increases, the impact of bond energy becomes more pronounced, resulting in an alloyed structure as the stable configuration. Furthermore, in cases where the proportion of Pd atoms is small, all Pd atoms are situated on the surface, displaying a discrete distribution morphology.