Abstract
Summary: We describe molecular dynamics simulations of Ξ±βtetrathiophene molecules deposited on a flat graphite substrate, at two different temperatures (300 K and 400 K) and several degrees of coverage (from approximately one to three molecular layers). The simulations employ a modified version of the CFF91 force field, with the torsion parameters tailored on highβlevel ab initio calculations on 2,2β²βbithiophene. We found that the molecules in the first layer were relatively planar and packed against the underlying surface, while those outside it were not arranged in wellβdefined layers and were more conformationally disordered. On the time scale of the simulation, the molecules did not crystallize but rather achieved a liquid crystallineβlike state with their average director parallel to the surface.
Side view of the final configuration in the simulation of 24 tetrathiophenes at 300 K. Molecules are depicted with different shades of gray according to their z coordinate (first, second or third layer).
imageSide view of the final configuration in the simulation of 24 tetrathiophenes at 300 K. Molecules are depicted with different shades of gray according to their z coordinate (first, second or third layer).