Evaluation of All-Atom Force Fields for Anthracene Crystal Growth

Abstract

Here we present a comprehensive evaluation of a set of well-known all-atom force fields with the scope to model dynamic phenomena in molecular crystals composed of polyaromatic hydrocarbons. The capability of the force fields to reproduce experimentally and computationally available data is thoroughly scrutinized against anthracene molecular crystals that serve as a model system. First, the properties of the solid crystalline phase are investigated by employing geometry optimization using molecular mechanics. Because any inaccuracies can be easily overlooked in the constrained solid crystalline phase, the interaction energy of a variety of dimer conformations is obtained by employing an extensive local minima search algorithm. The larger configurational freedom in the dimer conformations better reflects the incorporation of molecules at the surface during crystal growth. The results are compared to known ab initio calculations as very little experimental data concerning the anthracene dimer are available. Finally, for three force fields with different performance in other tests, a polymorph prediction is carried out. Overall, we show that some of the selected all-atom force fields (BMM2, BMM3, W99, and isoPAHAP) perform remarkably well, whereas others (Amber, Bordat, Dreiding, DRESP, MM2, and MM3) fail to reproduce known computational data for a variety of reasons.