Surface Structure of Bi(111) from Helium Atom Scattering Measurements. Inelastic Close-Coupling Formalism.

P Kraus,F Apolloner,Ch Gösweiner,W.E Ernst,S Miret-Artés,A Tamtögl,M Mayrhofer-Reinhartshuber

doi:10.1021/acs.jpcc.5b05010

Abstract

Elastic and inelastic close-coupling (CC) calculations have been used to extract information about the corrugation amplitude and the surface vibrational atomic displacement by fitting to several experimental diffraction patterns. To model the three-dimensional interaction between the He atom and the Bi(111) surface under investigation, a corrugated Morse potential has been assumed. Two different types of calculations are used to obtain theoretical diffraction intensities at three surface temperatures along the two symmetry directions. Type one consists of solving the elastic CC (eCC) and attenuating the corresponding diffraction intensities by a global Debye–Waller (DW) factor. The second one, within a unitary theory, is derived from merely solving the inelastic CC (iCC) equations, where no DW factor is necessary to include. While both methods arrive at similar predictions for the peak-to-peak corrugation value, the variance of the value obtained by the iCC method is much better. Furthermore, the more extensive calculation is better suited to model the temperature induced signal asymmetries and renders the inclusion for a second Debye temperature for the diffraction peaks futile.

Highlights

The electronic density structure of a surface determines its chemical behavior
Type one consists of solving the elastic CC and attenuating the corresponding diffraction intensities by a global Debye−Waller (DW) factor
The second one, within a unitary theory, is derived from merely solving the inelastic CC equations, where no DW factor is necessary to include. While both methods arrive at similar predictions for the peak-to-peak corrugation value, the variance of the value obtained by the iCC method is much better

Summary

Introduction

The electronic density structure of a surface determines its chemical behavior. While on surfaces like platinum, which is widely used as a catalyst, the effects of crystal face, surface steps, and kinks are well-known, more complicated electronic surface structures still lack a detailed treatment.

Results

Conclusion