A Structural and Stability Evaluation of Au12 from an Isolated Cluster to the Deposited Material

The morphology and charged state of gold clusters play a crucial role in heterogeneous catalysis. The selection and optimization of theoretical approaches are necessary for the investigation of active sites on isolated and supported gold clusters. In the present paper, a study of the potential isomers of the Au-12 cluster is performed within the DFT/PBE framework using a scalar-relativistic approach. We have found Au-12 to be a dynamic cluster with at least 24 isomers due to the Jahn-Teller distortion. The majority of these isomers exhibit low symmetry, resulting in the formation of low-coordinated atoms, which are discussed in terms of frontier molecular orbitals and a Hirschfeld analysis of their atomic charges. The energy difference between the most energetically stable 2D (D-3h) and 3D (C-2v) isomers of Au-12 is small (equal to 25 kJ/mol), which is evidence of their coexistence. The influence of the support on properties of the cluster is investigated using Au-12/MgO(100). The 2D isomer of Au-12 can interact with the surface either in an upright position, with two (E-ads/atom = 24 kJ/mol) or three atoms (E-ads/atom = 25 kJ/mol); the preferred position is planar (E-ads/atom = 30 kJ/mol). The small deformation energy is required to distort a dynamic structure of Au-12 compared to rigid gold clusters. The 3D isomer interacts with MgO(100) with two of its atoms (E-ads/atom = 24 kJ/mol). The Au-Au distances across the surface increase, whereas the Au-Au distances at an angle to the surface are compressed with respect to the distances in the free clusters. The weak adsorption energies of Au-12 on MgO and the low activation barriers for gold atom migration (15 kJ/mol) between oxygen sites facilitate the diffusion of nanoparticles on the MgO surface.