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Vibrational and Electronic Properties of acetylene, ethynyl and dicarbon chemisorbed on copper

We present a combined theoretical and experimental study of chemisorption parameters and STM images for C2H2, C2H, and C2 on Cu(001). The geometric and electronic structure, and vibrational energies were obtained from density functional calculations. The calculated STM images were obtained from Kohn-Sham wave functions using the Tersoff and Hamann approximation. A dramatically enhanced resolution in the experimental STM images were obtained using a tip that was obtained by irreversible dissociation of H2S. We find a near-quantitative agreement between experimental and calculated image for this tip and for a normal tip at appropriate tip-surface distances. An analysis shows that protrusions that appear in all images derive from adsorbate-induced resonances at the Fermi energy. All images also exhibit a wide depression that we attribute to the screening of the electronegative adsorbates by the metal conduction electrons.

DOI: 10.1021/jp025712l

View online : J. Phys. Chem. B 106, 8161 (2002)