Helium diffraction from adsorbate-covered surfaces: A study of the O-Ni(001) system

Elastic helium-atom surface scattering is currently being used to obtain important structural information from adsorbate-covered surfaces. Since our earlier work on helium diffraction from p(2×2) and c(2×2) phases of oxygen on Ni(001) there have been three new developments. These are (i) the suggestion by Rieder of a prolate charge distribution on oxygen, (ii) the pseudobridge site proposal of Demuth et al., and (iii) the self-consistent calculation of the helium-surface interaction potential due to Lang and Nørskov. In this paper we present results for a wide range of calculational parameters for the c(2×2) phase of oxygen on Ni(001) and comment on the above developments. Specifically, based on the results in (iii), we are able to explore the implications of the use of the Esbjerg- Nørskov-Lang relation with and without helium averaged surface-charge density. We conclude that the prolate charge distribution produces a shape function in better agreement with experiment. Changes in corrugation coefficients introduced by shifting to the pseudobridge site from the centered site are noted to be small. © 1984 The American Physical Society.