Observation of the low-energy external vibrations of benzene on Rh(111)

Quantitative Understanding of van der Waals Interactions by Analyzing the Adsorption Structure and Low-Frequency Vibrational Modes of Single Benzene Molecules on Silver

The combination of a sub-Kelvin scanning tunneling microscope and density functional calculations incorporating van der Waals (vdW) corrections has been used successfully to probe the adsorption structure and low-frequency vibrational modes of single benzene molecules on Ag(110). The inclusion of optimized vdW functionals and improved C6-based vdW dispersion schemes in density functional theory is crucial for obtaining the correct adsorption structure and low-energy vibrational modes. These results demonstrate the emerging capability to quantitatively probe the van der Waals interactions between a physisorbed molecule and an inert substrate.

Light-atom location in adsorbed benzene by experiment and theory

Locations of light atoms in C6D6 on Ru[0001] have been determined by low energy electron diffraction (LEED) and density functional theory (DFT). For the favored site/orientation in the p(square root of [7] x square root of [7])-R19 degrees phase, we find alternating outward bowing of the C-D bonds of 24 degrees and 9 degrees via LEED, and 22 degrees and 14 degrees via DFT. This remarkable agreement gives important cross confirmation of the validity of these techniques in describing the subtle contributions of light atoms to adsorbate scattering and energetics. The buckling is explained as a consequence of decreased aromaticity induced by the bonding to the substrate.