Density functional study of surface-supported planar magic Ag nanoclusters

Abstract

Experimentally, self-organized Ag planar clusters have been observed on the periodic template found on the Pb quantum islands, which are grown on the Si(111) surface. These planar clusters register a remarkable abundance variation at some specific atomic numbers and possess enhanced stability. They are thus denoted as two-dimensional magic Ag nanoclusters (or nanopucks). In this work, detailed calculations based on ab initio density functional theory are made to illuminate how the size and shape effects related to electronic confinement influence the sequence of these two-dimensional Ag nanostructures. The simulation results demonstrate that the evolution of a sequence of planar magic Ag clusters is strongly correlated with their electronic structures. Meanwhile, the role of substrate in the formation of magic Ag clusters is also examined. The symmetry and size of the periodic pattern on the substrate have helped to build up the distinguishable geometric structures in experiment. Further analysis of the related electronic and geometrical properties of these clusters not only explains the occurrence and sequence of the magic numbers but also helps to elucidate the mechanism of their formation.