Probing structural changes upon carbon monoxide coordination to single metal adatoms

Area of Science:

• Surface science
• Materials science
• Physical chemistry

Background:

• Understanding adatom behavior on oxide surfaces is crucial for catalysis and thin-film growth.
• Silver (Ag) adatoms on iron oxide (Fe3O4) surfaces are relevant for various catalytic applications.
• The interaction of adsorbates like carbon monoxide (CO) can significantly alter surface properties.

Purpose of the Study:

• To determine the adsorption height of silver adatoms bound to CO (Ag1CO) on a Fe3O4(001) surface.
• To compare the adsorption height of Ag1CO with that of bare Ag adatoms.
• To validate experimental findings with theoretical calculations.

Main Methods:

• Normal incidence X-ray standing waves (NIXSW) technique was employed to measure adsorption heights.
• Density Functional Theory (DFT) calculations, including van der Waals (vdW) and on-site Coulomb interaction (U) corrections, were utilized.
• Experimental substrate unit cell dimensions were fixed in the DFT calculations.

Main Results:

• Ag adatoms bound to CO (Ag1CO) were found to be lifted out of the surface.
• The measured adsorption height for Ag1CO was 1.15 Å ± 0.08 Å.
• This height is significantly greater than the 0.96 Å ± 0.03 Å for bare Ag adatoms.
• DFT+vdW+U calculations predicted an adsorption height of 1.16 Å for Ag1CO, showing excellent agreement with experimental data.

Conclusions:

• Carbon monoxide significantly influences the adsorption geometry of silver adatoms on Fe3O4(001).
• The NIXSW technique combined with DFT calculations provides accurate determination of adatom adsorption heights.
• The findings contribute to a fundamental understanding of adsorbate-surface interactions on magnetic oxide surfaces.