Reproducibility of Molecular Adsorption Potential Energy Surfaces

The adsorption of molecules on surfaces depends on a variety of mechanisms: Covalent bonds, charge transfer and van-der-Waals (vdW) interactions shape the potential energy surface (PES), making it key to understanding molecule-substrate interfaces. To describe these interfaces with density functional theory, one can choose from many different exchange correlation functionals and vdW correction schemes. To explore how robust the PES is in relation to the choice of method, we present a benchmark of common local, semi-local and non-local functionals in combination with various vdW corrections for perylenetetracarboxylic dianhydride (PTCDA) on Ag(111), one of the most frequently studied system.

Using only about 50 DFT calculations as input data, an in-house developed Gaussian process regression algorithm generates PESs with DFT accuracy. This allows us to analyze the PES’s features, such as positions and energies of minima and saddle points, in detail. Comparing the results from different exchange correlation functionals allows us to identify trends and differences between the approaches. Finally, we compare key features, such as local minima, with experimental data to determine a “quality seal” for the different functionals and vdW corrections.