# Dresden 2009 – wissenschaftliches Programm

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# O: Fachverband Oberflächenphysik

## O 25: Surfaces and films: forces, structure and manipulation

### O 25.2: Vortrag

### Dienstag, 24. März 2009, 15:15–15:30, SCH A118

**Energetics, electronic structure, and packing density of the Ir, Pt, and Au(100) surface reconstructions by all-electron DFT** — •Paula Havu^{1}, Ville Havu^{1}, Patrick Rinke^{1,2}, Volker Blum^{1}, and Matthias Scheffler^{1,2} — ^{1}Fritz-Haber-Institut der Max-Planck-Gesellschaft, D-14195 Berlin, Germany — ^{2}University of California at Santa Barbara, CA 93106, USA

Among fcc metals, only the late-5*d* transition
metals Ir, Pt, and Au rearrange by quasihexagonal reconstructions on
the nominally quadratic (100) surface structure. However, Ir reconstructs in one
direction only [(5×1)], while Au(100) and Pt(100) rearrange in
*both* lateral directions with large unit cells, often characterized as
(5× *N*) (*N*≥20 in the experimental literature). Elucidating the exact
packing density and energetics have been the focus of many experiments, but
theory has so far been relegated to either (5×1) approximants, or
simplified empirical potentials. Using *N* = 1, 10, 15, 20, 25,
30 supercell models (up to 786 atoms/cell) and the FHI-aims code [1], we
here show how all-electron
density-functional theory (DFT) captures the energetics, electronic structure, and
lateral packing densities of all three surfaces for different local-density
and generalized gradient approximations. Remarkably, the effect of the
2D reconstruction [(5× *N*) instead of (5×1)] on the surface
energy is nearly an order of magnitude bigger for Au than for Pt. DFT captures
quantitatively the energetically rather subtle difference in packing
densities, which is slightly higher for Au than Pt, consistent with experiment
[2]. [1] V. Blum *et al.*, Comp. Phys. Comm., accepted
(2008). [2] V. Jahns *et al*, Surf. Sci. **430**, 55 (1999).