Influence of Aggregate Shape and Exciton Location on Polarization Energy of Benzene and Anthracene Aggregates

To investigate the aggregate shape and exciton location on the polarization energies of benzene and anthracene aggregates, we performed calculations on the clusters in increasing size and differing shape. The results showed that the anthracene cluster showed no apparent difference in the shape dependence, however, benzene clusters differed significantly due to its nearest neighbors orient in a T-shape conformation compared to anthracene which is more stacked along its conjugated rings. Additionally, lower total energies of the ‘full’ model as well as less stable neutral energies for the surface molecules in the ‘intra+inter’ model suggest that the surface molecules interact repulsively. Due to the fact that the cube structure has a larger surface area to volume ratio and more benzene molecules are needed to take up said surface area more repulsive force may be experienced by molecules in the benzene cubes. Apparent polarization energy of each system increases as number of close by neighbors increases. Therefore molecules located centrally have larger induced dipole polarization as well as larger apparent polarization. Apparent polarization energy depends more sensitively on the location of the excitation than the shape of the cluster. Furthermore, the orientation of the nearest neighbors in each direction plays a large role in magnitude of the electrostatic interactions as well as the induced dipole effects.