Non-bonded force field for the interaction between metals and organic molecules: a case study of olefins on aluminum

In this work, we parameterize an empirical potential for the interaction between organic molecules and metal surfaces via force matching. This is done by pursuing a self-consistent approach similar to the ones used for equilibrium simulations; however, special attention is paid to the suitability of the resulting potential for tribological (non-equilibrium) situations. Specifically, we study olefin molecules confined between two aluminum surfaces under realistic pressures and shear rates. We find that the Buckingham potential produces better agreement with the first principle data than other force fields. While our training set only contains hexene molecules, we find that the standard error in the fitted olefin-aluminum interaction increases only by a factor of 1.15 when the force field is applied to butene, octene, and decene. Including mirror charges into the treatment only marginally improves fits. While olefins on aluminum is merely a special case, the proposed methodology can be used to parameterize any other interaction between polymers and metal surfaces for use in tribological simulations.