A re-examination of multilayer relaxation of Ag(110) by LEED structural analysis

Abstract

Although the existence of an oscillatory relaxation of the topmost two interlayer spacings of Ag(110) is well established by both low energy electron diffraction (LEED) and Rutherford backscattering spectroscopy (RBS) the magnitude of the first layer contraction and second layer expansion is still a matter of considerable dispute. In an attempt to clarify the situation we have performed an independent LEED study utilising a large normal incidence data set and 7 different reliability factors ( R-factors) to judge the level of theory-experiment agreement. The distance dz 12 between the first and second layers is smaller than the bulk interlayer distance by 7 ± 2% and the distance dz 23 between second and third layers is expanded by 1 ± 2%. Furthermore, a contraction of 2 ± 2% of the third interlayer spacing ( dz 34) has been extracted, with subsequent interlayer spacings equal to the bulk value within the precision of this analysis. These results are compared with theoretical embedded atom method and tight binding predictions of changes of up to the top four interlayer spacings. These results confirm and extend the surface geometry determined in an earlier LEED study of Davis and Noonan. Finally, the multilayer relaxations obtained by LEED are compared with recent RBS studies and possible reasons for discrepancies discussed.