Azobenzene at Coinage Metal Surfaces: The Role of Dispersive van der Waals Interactions

TL;DR

This study evaluates how different semi-empirical dispersion correction schemes affect the predicted adsorption geometries and energies of azobenzene on coinage metal surfaces, highlighting uncertainties due to damping functions.

Contribution

It compares various dispersion correction schemes in DFT calculations for azobenzene adsorption, revealing their impact and limitations in modeling van der Waals interactions.

Findings

Different schemes cause sizable changes in adsorption geometry and energy.

Results are sensitive to the damping function used in the correction.

Recent schemes tend to overbind compared to experimental data.

Abstract

We use different semi-empirical dispersion correction schemes to assess the role of long-range van der Waals interactions in the adsorption of the prototypical molecular switch azobenzene (C6H5-N2-C6H5) at the coinage metal surfaces Cu(111), Ag(111) and Au(111). Compared to preceding density-functional theory results employing a semi-local exchange and correlation functional we obtain partly sizable changes of the computed adsorption geometry and energetics. The discomforting scatter in the results provided by the different schemes is largely attributed to the unknown form of the damping function in the semi-empirical correction expression. Using the congeneric problem of the adsorption of benzene as a vehicle to connection with experiment, we cautiously conclude that the account of dispersive interactions at the metal surfaces provided by the various schemes is in the right ballpark, with the more recent, general schemes likely to overbind.