title: Calculating Optical Absorption Spectra of Thin Polycrystalline Organic Films: Structural Disorder and Site-Dependent van der Waals Interaction.
abstract: We propose a new approach for calculating the change of the absorption spectrum of a molecule when moved from the gas phase to a crystalline morphology. The so-called gas-to-crystal shift Δ[Formula: see text]mis mainly caused by dispersion effects and depends sensitively on the molecule's specific position in the nanoscopic setting. Using an extended dipole approximation, we are able to divide Δ[Formula: see text]m= -QWmin two factors, whereQdepends only on the molecular species and accounts for all nonresonant electronic transitions contributing to the dispersion whileWmis a geometry factor expressing the site dependence of the shift in a given molecular structure. The ability of our approach to predict absorption spectra is demonstrated using the example of polycrystalline films of 3,4,9,10-perylenetetracarboxylic diimide (PTCDI).
authors.affiliation: Institut für Chemie, Universität Potsdam , Karl-Liebknecht-Straße 24-25, D-14476 Potsdam, F. R. Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Megow
authors.affiliation: Institut für Chemie, Universität Potsdam , Karl-Liebknecht-Straße 24-25, D-14476 Potsdam, F. R. Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Körzdörfer
authors.affiliation: Institut für Theoretische Physik, Johannes Kepler Universität Linz , Altenberger Straße 69, A-4040 Linz, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Renger
authors.affiliation: Institut für Physik, Humboldt-Universität zu Berlin , Newtonstraße 15, D-12489 Berlin, F. R. Germany.
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authors.initials: M
authors.lastname: Sparenberg
authors.affiliation: Institut für Physik, Humboldt-Universität zu Berlin , Newtonstraße 15, D-12489 Berlin, F. R. Germany.
authors.forename: Sylke
authors.initials: S
authors.lastname: Blumstengel
authors.affiliation: Institut für Physik, Humboldt-Universität zu Berlin , Newtonstraße 15, D-12489 Berlin, F. R. Germany.
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authors.initials: F
authors.lastname: Henneberger
authors.affiliation: Institut für Physik, Humboldt-Universität zu Berlin , Newtonstraße 15, D-12489 Berlin, F. R. Germany.
authors.forename: Volkhard
authors.initials: V
authors.lastname: May
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