Interaction between Coronene and Graphite from Temperature-Programmed Desorption and DFT-vdW Calculations: Importance of Entropic Effects and Insights into Graphite Interlayer Binding

The adsorption of polycyclic aromatic hydrocarbon (PAH) molecules on graphitic surfaces provides a model system with which to investigate weak van der Waals (vdW) interactions. There are few experimental investigations of either the interaction between large PAH molecules and graphite or the binding between graphite layers. Determining the adsorption energy in these molecular systems provides a valuable benchmark for validating theoretical methods for implementing van der Waals interactions and, hence, also a means to investigate the interlayer binding in graphite. Here, we investigate the interaction between the coronene molecule and highly oriented pyrolytic graphite by using temperature-programmed desorption. We show how entropic effects play an important role in governing the desorption kinetics for large molecules such as coronene and must be taken into account in order to derive a realistic binding energy. DFT calculations demonstrate that the optB88-vdW functional is able to reproduce the experimentally derived binding energy. We use our experimental value to estimate the interlayer binding energy in graphite, considering the effect of intermolecular interactions found in the molecular system. The resulting value is again well reproduced by the optB88-vdW functional, indicating that the optB88-vdW functional is well-suited to describe the interaction between systems dominated by graphitic vdW interactions.