Non-magnetic and magnetic thiolate-protected Au25 superatoms on Cu(111), Ag(111) and Au(111) surfaces

摘要

Geometry, electronic structure, and magnetic properties ofmethylthiolate-stabilized Au$_{25}$L$_{18}$ and MnAu$_{24}$L$_{18}$ (L =SCH$_3$) clusters adsorbed on noble-metal (111) surfaces have been investigatedby using spin-polarized density functional theory computations. The interactionbetween the cluster and the surface is found to be mediated by charge transfermainly from or into the ligand monolayer. The electronic properties of the13-atom metal core remain in all cases rather undisturbed as compared to theisolated clusters in gas phase. The Au$_{25}$L$_{18}$ cluster retains a clearHOMO - LUMO energy gap in the range of 0.7 eV to 1.0 eV depending on thesurface. The ligand layer is able to decouple the electronic structure of themagnetic MnAu$_{24}$L$_{18}$ cluster from Au(111) surface, retaning a highlocal spin moment of close to 5 $\mu_{B}$ arising from the spin-polarizedMn(3d) electrons. These computations imply that the thiolatemonolayer-protected gold clusters may be used as promising building blocks withtunable energy gaps, tunneling barriers, and magnetic moments for applicationsin the area of electron and/or spin transport.