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SYOF: Organische Festkörper

SYOF 5: Poster Session

SYOF 5.36: Poster

Dienstag, 27. März 2001, 17:00–19:00, Aula S3

Electronic band structure and intermolecular interaction in substituted thiophene polymorphs — •J. Widany¹, G. Daminelli¹, A. Di Carlo¹, P. Lugli¹, G. Jungnickel², M. Elstner², and T. Frauenheim² — ¹Dipartimento di Ingegneria Elettronica, Università di Roma II “Tor Vergata”, I-00133 Roma, Italy — ²Theoretische Physik, Fachbereich Physik, Universität-Gesamthochschule, D-33098 Paderborn, Germany

Total energy calculations based on a density-functional tight-binding scheme have been performed on polymorphic modifications of various thiophene crystals (β- tetra-methylsulphanyl)- α-quaterthiophene and (β- tetramethyl) -α-sexithiophene. The electronic band structures exhibit a quasi one dimensional interaction in the triclinic crystals, while the monoclinic modifications show no dispersion over the whole Brillouin zone. The main interaction mechanism can be described as a d−π wave function overlap between sulphur and carbon. The strong intermolecular interaction may induce an inter-chain excitation, responsible for the different optical properties of the polymorphs.