Structural precursor to adsorbate-induced reconstruction: C on Ni(100)

Abstract

The local structure around adsorbed carbon atoms on Ni(100) has been determined at low coverage as well as in the 0.5 monolayer $(2\ifmmode\times\else\texttimes\fi{}2)p4g$ ``clock'' reconstruction by scanned energy mode photoelectron diffraction. At low coverage, there is no radial strain of the Ni atoms surrounding the adsorbed carbon, contrary to previous suggestions. None of the C-Ni near-neighbor distances are changed by reconstruction, but the Ni-Ni nearest-neighbor distance in the top layer increases significantly, showing that the adsorbate-induced compressive stress is associated with Ni-Ni, rather than Ni-C, repulsion.