Tersoff-Hamann and Bardeen perturbation theory derived empty-state STM images of the [4 + 2] intradimer adduct of 1,3-cyclohexadiene (CHD) adsorbed on Si(100)-2 × 1 using a density functional description of the electronic structure appear to capture the π* CdC orbital observed experimentally but ultimately produce images dominated by the CH2 groups. Neither averages over finite temperature structures nor use of W(110) tips with O or Si adsorbed on the apex yield the correct image. Strong tip-CHD interactions substantially lower the energy of the π* orbital relative to the Fermi energy and change the CHD geometry. In addition to perturbing the CdC bond, it is found that the tip pushes aside the CH2 groups. The former electronic effect enhances the prominence of the π* orbital, while the latter geometric effect suppresses contributions from the remainder of the CHD.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films