Energies and Alignment of Conjugated Molecules in the External Fields
Y. Kabashi, S. Kabashi
University of Prishtina, Faculty of Mathematics and Natural Sciences, Department of Physics, Prishtina, Kosovo
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This paper reports theoretical works based on experiments studying the formation and structure of thin films of a number of different organic molecules, particularly pentacene and a number of its functionalized variants and analogs on non-metallic substrates such as KCl. The molecules that form the films studied are anisotropic planar molecules (i.e., they have the geometry, roughly, of domino tiles) of similar dimensions, but different charge distributions and free chemical bonds. In the films, these varying properties lead to different stacking schemes, including herringbone upright stacking, slip-stack stacking of flat-lying molecules, and cross-cross packing of molecules lying upright on the long edge. The energies of these planar organic molecules are studied in the presence of an electric field generated due to the surface charging. Then the energies of domino-shaped organic molecules are calculated in homogeneous and inhomogeneous electric fields, which model uniformly and non-uniformly charged substrates, respectively. The relevant properties of the molecules are given by the polarizability tensors and the quadrupole tensors of the respective molecules. These calculated elements of these two tensors are used to calculate the dipole and quadrupole contributions to their electrostatic energies in uniform electric fields and in non-uniform electric fields of point-charge form.

topics: organic molecules-pentacene, homogeneous and inhomogeneous electric field, energies, alignment