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O: Fachverband Oberflächenphysik

O 64: New Methods

O 64.5: Poster

Mittwoch, 18. März 2015, 18:15–21:00, Poster A

An approximative method to tackle the modeling of thin film IR spectra — •Jochen Vogt — Chemisches Institut der Uni Magdeburg, Magdeburg, Germany

A vibrational analysis of molecular adlayers based on the calculation of the full Hessian within DFT or other ab initio theory is frequently a computationally expensive task. In order to tackle the modeling of IR spectra of thin films with large unit cells, an approximative method is investigated. It is based on the first principles calculation of the Hessians and dipole derivative tensors of individual molecular entities or small clusters using large basis sets. These partial Hessians are used in the second step to reconstruct the full Hessian. The off-diagonal elements representing the intermolecular vibrational coupling are built from the partial dipole derivative tensors assuming that dipole-dipole interaction is the leading coupling term. The inclusion of other types of interaction, however, is possible. First results indicate that calculated Davydov splittings due to dynamic dipole-dipole coupling are larger than observed in experiments and thus require the inclusion of a suitable scheme of electrostatic damping [1].
J. Salas et al., J. Chem. Phys. 133 (2010), 234101