Development of classical molecule-surface interaction potentials based on density functional theory calculations: investigation of force field representability

A simple classical force field, based only on Coulomb and Lennard-Jones potentials, was developed to describe the interaction of an ethanol molecule physisorbed on the a-alumina (0001) surface. A range of adsorption structures were calculated using density functional theory (DFT) and these results were used for the force field parametrization. This system has a very inhomogeneous adsorption energy landscape, and the importance of the choice of data set used for fitting the force field was investigated. It was found that a Lennard-Jones and Coulombic potential can describe the ethanol-alumina interaction in reasonable qualitative agreement with the OFT reference data, provided that the data set was representative of both short- and long-range interactions and high- and low-energy configurations. Using a few distance-dependent adsorption energy curves at different surface sites gives the best compromise between computing time and accuracy of a Lennard-Jones based force field. This approach demonstrates a systematic way to test the quality of a force field and provides insight into how to improve upon the representability for a complex adsorption energy landscape.