DFT global optimisation of gas-phase and MgO-supported sub-nanometre AuPd clusters.

Heider A Hussein,Roy L Johnston,Jack B A Davis

doi:10.1039/c6cp03958h

Abstract

The Birmingham Parallel Genetic Algorithm (BPGA) has been adopted for the global optimization of free and MgO(100)-supported Pd, Au and AuPd nanocluster structures, over the size range N = 4-10. Structures were evaluated directly using density functional theory, which has allowed the identification of Pd, Au and AuPd global minima. The energetics, structures, and tendency of segregation have been evaluated by different stability criteria such as binding energy, excess energy, second difference in energy, and adsorption energy. The ability of the approach in searching for putative global minimum has been assessed against a systematic homotop search method, which shows a high degree of success.

Highlights

Nanomaterials have at least one dimension on the nanometer scale (1–100 nm)
Global minima for the gas phase Pd clusters are all found to be different from their supported structures with the exception of Pd4 which remains a tetrahedron
We have previously presented BCGA-DFT studies of free Pd8, Pd9, and Pd10 clusters,[16,48] whose putative global minima were identified as a dodecahedron, an icosahedral fragment, and an incomplete centered icosahedron, respectively

Summary

Introduction

Nanomaterials have at least one dimension on the nanometer scale (1–100 nm) They have recently emerged as new materials that bridge the gap between atoms or molecules and bulk materials, and they have attracted remarkable interest owing to their numerous potential applications.[1] Nanomaterials contribute to many new technological applications in various fields, such as medicine, materials, physics, and chemistry. These new applications came as a consequence of their novel chemical and physical properties which are due to electronic and quantum effects and the high surface-area-to-volume ratio.[1,2,3]. AuPd catalysts have been found to be promising candidates for a wide variety of chemical reactions, such as cyclohexane oxidation,[8] NO reduction,[9] CO oxidation,[10,11] direct synthesis of hydrogen peroxide,[12,13] and synthesis of aldehydes from primary alcohols.[14]

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Conclusion