Dresden 2011 – scientific programme
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O: Fachverband Oberflächenphysik
O 102: Epitaxy and growth: Metals and semiconductors II
O 102.3: Talk
Friday, March 18, 2011, 11:45–12:00, WIL C307
DFT studies of small metal ad-atom clusters on fcc(111) surfaces — •Andreas Garhofer1,2, Claudia Lenauer2, Florian Wimmer2, Philipp Scheiber2, Michael Schmid2, Peter Varga2, and Josef Redinger1,2 — 1Computational Materials Science TU Wien, Vienna, Austria — 2Institute for Applied Physics TU Wien, Vienna, Austria
Bonding of face-centered-cubic metals is usually characterized by a preference of a high coordination number for each atom. However by creating a large amount of Pt clusters with pulsed laser deposition on a Pt(111) surface, up to 1/3 of all clusters were found to be linear chains with lengths of up to 9 atoms. We studied different Pt ad-atom arrangements on Pt(111) with first principles DFT methods and found that for 3 and 4 ad-atom structures a linear chain is most stable. A three atom Pt chain is also more stable than a triangular configuration on other substrates such as fcc Rh(111), Pd(111), Ir(111), Au(111) and hcp Ru(0001), which all have similar lattice constants to Pt(111). For the homoepitaxial systems of these transition metals, only the 5d elements form stable linear ad-atom arrangements i.e. only Ir on Ir(111), Pt on Pt(111) and Au on Au(111). The main reason for the stabilization of the ad-atom chain is a strong dz2 orbital interaction, which pushes the corresponding antibonding state above EF. The formation of longer Pt chains as seen by experiment on Pt(111) is due to steering by lower diffusion barriers towards the end of the chain.