Gauthier, Y.; Moritz, Wolfgang; Hösler, W.
Surface alloy in the c(4 × 4) phase of Pb on Cu(100).
In: Surface Science, Vol. 345, Nr. 1-2: S. 53-63
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The structure of the c(4 × 4) phase of Pb on Cu(100) has been determined by a LEED I/V analysis. The characteristic feature of this structure are Pb chains along the close packed rows with Cu chains between the Pb chains. The surface layer is an ordered alloy layer with 3 Pb and 4 Cu atoms in the primitive unit cell, the Pb coverage is 0.375 monolayers. The Pb-Pb distance within the chain is 3.4 Å and 2.8\% smaller than the distances in bulk Pb. The Pb chain is slightly corrugated by 0.05 Å where one of the three Pb atoms is in a hollow site of the substrate. Due to the smaller atomic radius the Cu chain is 0.65 Å below the Pb site. Half of the Cu atoms are shifted by 0.23 Å off the fourfold sites such that roughly the same distance to the surrounding Pb atoms in the top layer is maintained. The Pb-Cu bond length varies slightly at different sites around 2.9 Å.