FIRST PRINCIPLES DENSITY FUNCTIONAL INVESTIGATION OF SUPPORTED TUNGSTEN CLUSTER (W_n; n = 1 TO 6) ON ANCHORED GRAPHITE (0001) SURFACE

摘要

Size-selected W_n clusters can be deposited firmly on a graphite (0001) surface using a novel technique, where the positive ions (of the same metal atom species) embedded on the graphite surface by ion implantation, act as anchors. The size selected metal clusters can then soft land on this anchored surface m [Hayakawa et al., 2009). We have carried out a systematic theoretical study of the adsorption of W_n (n = 1-6) clusters on anchored graphite (0001) surface, using state-of-art spin-polarized density functional approach. In our first-principles calculations, the graphite (0001) surface has been suitably modeled as a slab separated by large vacuum layers. W_n clusters bond on clean graphite (0001) surface with a rather weak Van-der-Waals interaction. However, on the anchored graphite (0001) surface, the W_n clusters get absorbed at the defect site with a much larger adsorption energy. We report here the results of our first-principles investigation of this supported W_n cluster system, along with their reactivity trend as a function of the cluster size (n).