Molecular dynamics simulations of pentacene thin films: The effect of surface on polymorph selection

Molecular dynamics simulations were performed for multi-layer pentacene thin films using a simple model surface. Two pentacene polymorphs, low-temperature (LT) and high-temperature (HT), were compared by examining their stability on a substrate and under free surface conditions. It was found that the LT polymorph was destabilised by the presence of substrate and free surface effects, which transformed the HT-polymorph over the course of our simulations. Suppression of the molecular fluctuations along the long molecular axis by these surface effects was suggested as the source of this destabilisation.