Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 65: Density functional theory and beyond for real materials III

O 65.7: Talk

Thursday, March 25, 2010, 12:00–12:15, H34

A DFT study on electronic structure and vibronic properties of d⁸ (Ni-, Pd-, and Pt-) phthalocyanines — •Davoud Pouladsaz¹, Thiruvancheril G. Gopakumar², and Michael Schreiber¹ — ¹Institut für Physik, Technische Universität Chemnitz — ²Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel

We studied the HOMO-LUMO gap shrinking in order to investigate the tip-induced polarization in scanning tunneling spectroscopy of d⁸ (Ni, Pd, and Pt) phthalocyanines [1]. By means of density functional theory (DFT), the molecular orbital energies have been calculated for Ni-, Pd-, and PtPc single neutral molecules and singly and doubly ionized cations and anions of all molecules. Interestingly, the position of the HOMO decreases systematically with increasing the atomic number of the central metal atom. The first ionization energies of neutral molecules increase by changing the central metal atom, while the electron affinities remain constant. This causes an increase in the HOMO-LUMO gap. These results show a clear correlation to experimental observations. Furthermore, we performed a DFT study on photoelectron spectra of the first and the second ionizations of these molecules, computing the vibronic couplings and the reorganization energies. The partitioning of the reorganization energy into normal mode contributions shows that the major contributions are due to several vibrational modes with a_1g symmetry lower than 1600 cm⁻¹.

[1] Th. G. Gopakumar, J. Meiss, D. Pouladsaz, and M. Hietschold, J. Phys. Chem. C, 112, 2529 (2008)