Theoretical structure investigations of gold nanoparticles on a stepped magnesium oxide surface
Final Report Abstract
The presence of a monoatomic step layer alters the shape, the orientation and the energetic ordering of structural motifs for gold clusters that have been found on the corresponding flat, defect-free (001) magnesium oxide surface. For small cluster sizes quasi-planar and inclined as well as arched leaflet structures are energetically preferred at the step, whereas vertical leaflets prevail on the flat surface. These characteristics are due to the non-symmetric environment induced by the step atoms. While tetrahedral structures dominate for clusters consisting of seventeen up to twenty atoms on the flat surface, hollow cage structures clearly persist on the stepped surface. These structures enhance their stability to a great extent because of their ability to bind to a maximum number of substrate and step oxygen atoms. An exception with a remarkable stability on the stepped surface is a tetrahedron with twenty gold atoms. For up to twenty-four atoms a competition between cage structures and leaflets exists. The structure database that has been created in this study, especially on a more realistic defect surface, may serve for further investigations in heterogeneous catalysis. Special requirements for cluster stability on the stepped surface as well as limitations for further cluster constructions are discussed. Preliminary results for small gold-palladium alloys on the same stepped substrate are also presented in order to elucidate first preferential arrangements. Finally, some other structural investigations for NiMg clusters in gasphase have also been done performing global optimization techniques using the basin hopping method. Appropriate parameters in the atomistic potential have been searched for in these clusters in order to result in reliable structural tendencies.
Publications
- ’Determination of the structures of small gold clusters on stepped magnesia by density functional calculations’, Nanoscale 4:1101, 2012
K. Damianos and R. Ferrando
