Structural Study of the Ni{100}−(2 × 2)-C Surface by Time-of-flight Scattering and Recoiling Spectrometry

Abstract

The structure of the Ni{100}-(2 × 2)-C surface has been investigated by time-of-flight scattering and recoiling spectrometry (TOF-SARS), low-energy electron diffraction (LEED), and classical scattering simulations. The surface was prepared by chemisorption of either carbon monoxide, benzene, or aniline onto a Ni{100} surface at 600°C. The scattering flux from 4 keV of Ne + and the recoiling flux of carbon from 4 keV of Ar + were monitored as a function of the crystal azimuthal angle. An efficient simulation method, which is based on the binary collision approximation and shadowing and blocking effects, has been developed and applied to simulation of the TOF-SARS azimuthal scans. Quantitative values for the geometrical parameters were obtained by using a reliability (R) factor to compare the experimental and simulated azimuthal scans. The results are consistent with a surface structure which consists of 80% of a clock reconstructed (2 × 2)p4g phase and 20% of an unreconstructed (2 × 2) phase. For the reconstructed phase, the Ni atoms rotate in alternating clockwise and anticlockwise directions with the Ni atoms displaced laterally from their original positions by 0.6 ( 0.1 Å and the C atoms in the 4-fold sites at positions 0.1 ( 0.1 Å above the plane of Ni atoms. The consequences of these results with respect to heterogeneous catalysis are discussed.

The role of interfacial strain in the surface p4g reconstruction: a comparison between and

“…The azimuthal angle φ scan in ion scattering is well suited for demonstrating this fact. For the (2 × 2)p4g surface, the agreement between the experimental and simulated φ scans was judged on the basis of the reliability R factor [14,15]. Simulations for the (2×2)p4g surface were carried out as a function of the Pd lateral displacement ( x) from 0.1 to 1.0 Å in steps of 0.1 Å. R factors were calculated for comparison of each of the simulated φ scans with the experimental data.…”

Surface Study of Ni₂MnGa(100)

“…Thus, the Ni 2 MnGa (100) surface reconstructs to lower symmetry p4gm space group. Such reconstruction has been observed in Pd/Cu surface alloy [36], on Ni(100) by deposition of carbon [37,38] and recently in Ca 2-…”

“…Generally, the reduction of symmetry from p4mm to p4gm is associated with rotation of surface atoms. For example, deposition of carbon on Ni(100) results in rotation of the Ni atoms surrounding the fourfold hollow adsorption sites of carbon resulting in p4gm reconstruction [37,38]. In Ca 2-x Sr x RuO 4 (001), rotation of the RuO 6 octahedra has been shown to be the reason for p4gm symmetry [39].…”