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M: Metallphysik

M 32: Poster TU B (Symposium Tomographic Methods in Materials Research M-32.32-55)

M 32.11: Poster

Montag, 7. März 2005, 14:30–16:30, Poster TU B

DFT investigation of free and supported Mo_mS_n clusters — •Sibylle Gemming, Igor Popov, Jelena Tamuliene, and Gotthard Seifert — Institut für Physikalische Chemie, TU Dresden, D-01062 Dresden

The electronic and structural properties of clusters (Mo_n S_m ) of the layered semiconductor MoS₂ were studied using density-functional based methods. For small Mo_nS_m clusters the evolution of structural elements, resembling the corresponding structure motifs of the layered bulk compound MoS₂ was found. Among the small clusters a highly symmetric Mo₄S₆ cluster features an outstandingly high stability and a large HOMO-LUMO gap. Thus, this cluster can be characterized as a ”magic cluster”. Mo₄S₆ forms stable, regular arrays on the Au(111) surface with a preferential adsorption of three sulphur atoms at Au-Au bridging positions. With increasing cluster size the stabilization of platelet structures is indicated. In the platelet structures the edges determine the deviation from the bulk properties. The binding energies increase smoothly with increasing cluster size towards the bulk limit. Small clusters and platelet structures have a HOMO-LUMO gap comparable with the gap of the semiconductor bulk material, whereas larger platelet structures show a metallic-like behaviour.