A LEED structural study of the Pd{110}-(1×1) surface and an alkali-metal-induced (1×2) surface reconstruction

Abstract

From a LEED study of the {110} surface of palladium it was concluded that an oscillatory relaxation occurs with respect to the bulk interlayer spacing in the top two layers of a laterally unreconstructed surface. The first and second interlayer spacings were found to be -6±2% and 1±2%, respectively, with respect to the bulk value. These results compare with recent embedded atom theory predictions that a first layer contraction of ∼11% occurs. Low coverages of the alkali metals Cs and Na are shown to induce a (1×2) reconstruction of the Pd{110} surface. We present details of coverage and alkali metal dependence of the (1×1) to (1×2) phase transition. A LEED study has been carried out to examine the feasibility of a wide range of possible structures exhibiting the required lateral periodicity. We favour models in which all selvedge atoms remain at or near bulk-like positions, the "missing row" and "saw-tooth" models being the most satisfactory so far tested. © 1985.