Free gold clusters: beyond the static, monostructure description

Abstract

The thermodynamical stability of free, pristine gold clusters at finite temperature, and of cluster+ligands complexes at finite temperature and in the presence of an atmosphere composed of O2 and CO, is studied employing parallel tempering and ab initio atomistic thermodynamics. We focus on Au13, which displays a significant fluxional behavior: Even at low temperature (100 K) this cluster exhibits a multitude of structures that dynamically transform into each other. At finite temperature, the preference of this cluster for three-dimensional versus planar structures is found to result from entropic effects. For gold clusters containing one to four gold atoms in an O2 + CO atmosphere, we apply ab initio atomistic thermodynamics. On the basis of these considerations, we single out a likely reaction path for CO oxidation catalyzed by gold clusters.

σ-Holes on Transition Metal Nanoclusters and Their Influence on the Local Lewis Acidity

“…The Pt 13 structure cannot be easily categorized, but comprises atoms with a relatively open arrangement [14]. Au 13 has a slightly more compact structure based on a prism Au 6 core with capping Au atoms arranged around it [19,[21][22][23]. It should, at this point, be noted that 3D Au 13 nanoclusters are only stable with respect to 2D clusters if valence electron spin-orbit effects are accounted for [14].…”

“…The initial geometries for the Au 13 , Cu 13 , Pt 13 , Pt 7 Cu 6 , Pd 13 , Co 13 , Ir 13 , Rh 13 , and Ru 13 TM nanoclusters were taken from documented low-energy structures ( Figure 2) [14][15][16][17][18][19][20][21][22][23]. These were reoptimized under symmetry constraints in the Turbomole 6.4 software package [13] using the Def2-TVZP basis set; the Def2 basis set family of Ahlrichs and co-workers [12] employs effective core potentials (ECPs) for the 4d and 5d, but not for the 3d metals.…”

“…In the present work, we shall investigate the presence and absence of the various kinds of σ-holes on a series of neutral, low-energy TM 13 nanoclusters [14][15][16][17][18][19][20][21][22][23]. The nanoclusters comprise the mixed elemental Pt 7 Cu 6 nanocluster as well as the Ir 13 , Pt 13 , Au 13 , Pd 13 , Rh 13 , Ru 13 , Cu 13 and Co 13 clusters.…”

Die CO‐Oxidation als Modellreaktion für heterogene Prozesse

“…Neutrale Goldcluster wurden in einer Gasphase modelliert, mit variablen Kompositionen von CO und O 2 im Temperaturbereich von 100-600 K mithilfe von DFT-Rechnungen in Verbindung mit der thermodynamischen Ab-initioTechnik. [79] Vergleicht man CO-und O 2 -Adsorption, haben Goldcluster eine deutliche Präferenz, stärker CO als O 2 zu binden. Sind jedoch beide Liganden gleichzeitig in der Gasphase vorhanden, die den Cluster enthält, findet ein kooperativer Adsorptionseffekt statt, und die bevorzugten Produkte sind solche, die sowohl CO als auch O 2 enthalten.…”

Gold-platinum alloys and Vegard's law on the nanoscale

“…Nanoparticles (NPs) made of noble metals have proven to be excellent catalysts. [1][2][3][4][5][6][7][8] Alloy particles from gold (Au) and platinum (Pt) are of particular interest, as they show enhanced catalytic behavior in important oxidation reactions. [9][10][11][12][13][14][15][16][17] They allow these reactions to take place under mild conditions, thus offering hope for materials' synthesis with minimal ecological impact.…”