Hamburg 2001 – wissenschaftliches Programm
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SYOF: Organische Festkörper
SYOF 5: Poster Session
SYOF 5.4: Poster
Dienstag, 27. März 2001, 17:00–19:00, Aula S3
Density functional calculations of the vibrational properties of 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) monoclinic crystals — •R. Scholz1, J. Widany2, M. Elstner3, and T. Frauenheim3 — 1Institut für Physik, Technische Universität, D-09107 Chemnitz, Germany — 2Dipartimento di Ingegneria Elettronica, Università di Roma II “Tor Vergata”, I- 00133 Roma, Italy — 3Theoretische Physik, Fachbereich Physik, Universität-Gesamthochschule, D-33098 Paderborn, Germany
The vibrational properties of a prototypical organic semiconductor, PTCDA, are analysed with a density functional tight-binding calculation, both for the isolated molecule and the monoclinic bulk phase. Concerning the model calculation of the bulk crystal, we investigate in detail how van der Waals corrections to the total energy affect the relaxed geometry of the two molecules in the crystal unit cell. Moreover, we studied the adsorption of PTCDA monolayers on graphite with respect to geometry changes of the molecule and the interlayer distance.
Our resulting vibrational spectra for the monoclinic crystal and the isolated molecule are compared with existing experimental evidence concerning Raman and infrared observations. Various details, e.g. Davydov splitting of polar and non-polar vibrations, and the positions of external Raman-active phonon modes, are in good agreement with the experimental findings.