Abstract
The surface mode of the Birmingham Cluster Genetic Algorithm (S-BCGA), which performs an unbiased global optimisation search for clusters adsorbed on a surface, has been employed for the global optimisation of noble metal pentamers on an MgO(1 0 0) substrate. The effect of element identity and alloying in surface-bound neutral subnanometre particles is calculated by energetic analysis of all compositions of supported 5-atom PdAu and PdPt clusters. Our results show that the binding strengths of the component elements to the surface are in the order Pt > Pd > Au. In addition, alloying Pd with Au and Pt is favorable for this size since excess energy calculations show a preference for bimetallic clusters for both cases. Furthermore, the electronic behaviour, which is intermediate between molecular systems and bulk metals allows tuning of the characteristics of particles in the subnanometre size range. The adsorption of CO and O2 probe molecules are also modelled and it is found that CO and O2 adsorption leads to a weakening of the cluster–surface interaction.
Highlights
The adsorption of transition metal clusters and nanoparticles supported on oxide surfaces includes materials with varied technological applications in microelectronic components [1], metal-ceramic composites [2], gas sensors [3], corrosion protection [4], and heterogeneous catalysis [5]
Gamma point calculation have been used for a wide range of studies of MgO-supported clusters and we have found gamma-point Density Functional Theory (DFT) calculations to be sufficient for this study
All single metal atoms favor atop oxygen binding site on the MgO substrate and the calculated interaction energies are: 0.95 eV (Au); 1.42 eV (Pd) and 2.42 eV (Pt), which are in excellent agreement with previous calculations [52,53,54]
Summary
The adsorption of transition metal clusters and nanoparticles supported on oxide surfaces includes materials with varied technological applications in microelectronic components [1], metal-ceramic composites [2], gas sensors [3], corrosion protection [4], and heterogeneous catalysis [5]. In these applications, understanding of supported small (subnanometre) metal clusters is aided by study of cluster nucleation and growth, mobility and catalytic activity.
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