Structure and melting of small Ni clusters on Ni surfaces

Abstract

Using the Voter and Chen (VC) version of the embedded atom model (EAM), we performed computer simulations to obtain the structures and binding energies of small Ni clusters on Ni(001), Ni(110) and Ni(111) surfaces. The predicted Ni cluster structures on Ni(001) and Ni(111) generally agree with the results obtained by Liu and Adams using the Foiles, Baskes and Daw (FBD) version of the EAM (the only exception is one structure formed on the Ni(001) surface), but the corresponding binding energies differ significantly. The temperature dependence of the behaviour of the seven-atom Ni cluster on the Ni(111) surface shows that the predicted cluster melting temperature also depends significantly on which version of the EAM is used. Hence EAM predictions of the properties of supported metal clusters depend crucially on the parameterization of the model, i.e. on the kind of data used in optimizing the embedding function and pair interaction. Although ab initio results for Ni clusters on Ni surfaces are not available for comparison, it seems plausible that the EAM description of supported transition metal clusters, like the EAM description of free transition metal clusters, may in general be more accurate if the VC version of the model is used rather than the FBD version since the former uses diatomic data as well as bulk properties in optimizing the EAM functions, and its parameterization should therefore be more appropriate for the cluster level.