A molecular dynamics study of the effect of pentacene polymorphs on C60 surface adsorption and diffusional properties and the tendency to form nanowires

Using atomic-scale molecular dynamics and energy minimisation techniques with semi-empirical molecular mechanics 3 potential energy functions, we consider the adsorption of a C-60 molecule on pentacene in the known thin film and bulk phases and a series of hypothetical, variably angled, pentacene structures. The thin film phase has a more energetically isotropic surface than the bulk, and exhibits diffusion coefficients that are twice as high, potentially leading to preferable characteristics for ordered film growth. For the variably angled pentacene structures, where the long axis is parallel to the substrate, a relationship was discovered between the angle that the pentacene short axis makes with the surface normal (controlled by the underlying substrate) and the adsorption characteristics of C-60. There is a transition of the dominant energy minima from between the pentacene rows at low values of phi(1) to within the rows at high values of phi(1), where phi(1) is the angle the bottom pentacene short axis makes with the surface normal. This shift implies that the likelihood of forming C-60 nanowires on pentacene is greater at extreme values of phi(1) for which there would be a clear preference for C-60 to be located between a row or within a row, rather than at intermediate values of phi(1), where there is no clear preference.