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O: Fachverband Oberflächenphysik

O 14: Metal Substrates: Epitaxy and Growth

O 14.11: Talk

Monday, March 26, 2007, 16:45–17:00, H39

Atomic distribution in 2D surface alloys - linking STM results with DFT studies via effective cluster interactions — •Andreas Bergbreiter¹, Harry E. Hoster¹, Yoshihiro Gohda², Axel Groß², and R. Jürgen Behm¹ — ¹Institut für Oberflächenchemie und Katalyse, Universität Ulm, 89069 Ulm — ²Institut für Theoretische Chemie, Universität Ulm, 89069 Ulm

Surface alloys such as Pt_xRu_1−x/Ru(0001), Pd_xRu_1−x/Ru(0001), Cu_xPd_1−x/Ru(0001), or Au_xPt_1−x/Pt(111) are governed by a local equilibrium [1,2], i.e., intermixing is confined to the outermost layer, and the lateral atomic distributions depend on the intermetallic interactions. These can be described by an Ising type Hamiltonian based on effective cluster interactions (ECIs). From atomically resolved STM images of the distinct surface alloys we have derived ECIs by an Inverse Monte Carlo approach. Complementary, the respective parameters can also be derived from energies attained for ordered surface alloys of varying unit cell compositions and geometries via Density Functional Theory (DFT). This allows us to compare theoretically predicted with experimentally found atomic distributions of systems without long-range order.

[1] A.V. Ruban et al., in Surface Alloys and Alloy Surfaces, Vol. 10, (ed.: D. P. Woodruff), Elsevier; Amsterdam 2002, pp. 1-29.

[2] H.E. Hoster, E. Filonenko, B. Richter, R.J. Behm, Phys. Rev. B 73 (2006) 165413.