Photoionization cross-section weighted DFT simulations as promising tool for the investigation of the electronic structure of open shell metal-phthalocyanines

Abstract

The valence band structure of different metal-phthalocyanines was investigated by comparing ultraviolet photoelectron spectra at different excitation energies with simulated spectra that take the different photoionization cross-sections at these energies into account. The Kohn-Sham eigenvalue spectra, derived from density functional theory calculations, using hybrid exchange-correlation functionals, were weighted with the photoionization coefficients in accordance with the used excitation energy. By applying these techniques, the differences in the photoelectron spectra using He I and He II radiation can be reproduced and investigated. It will be shown that the 3d-orbitals of the used metal central atom of these molecules have a major influence. The changes at different excitation energies were studied for Fe, Co, and Cu central atoms to describe the chemical tailoring effects.

Electronic structure of copper phthalocyanine fromG0W0calculations

“…101,102 We conducted G 0 W 0 calculations of CuPc, based on both PBE and PBEh (denoted throughout as GW@PBE and GW@PBEh, respectively) with increasingly large hierarchically constructed NAO basis sets 103 and compared the resulting QP HOMO energy to the experimental ionization potential (IP) value of 6.38 eV, obtained from gas phase UPS. 2,3,5 The results are shown in Figure 2. The largest change in the QP HOMO energy is from tier 1 to tier 2.…”

“…It is even a candidate for single molecule devices. 1 Owing to these applications, there is considerable interest in investigating its electronic structure, both experimentally [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and theoretically. 2,3,10,16,[20][21][22][23][24][25][26][27][28][29][30][31] Beyond its technological relevance, CuPc is a prototypical molecule representative of typical interactions in many metal-organic systems and therefore an excellent benchmark for evaluation of computational methods.…”

Benchmark ofGWmethods for azabenzenes

“…We note that the comparison of the calculated spectra to PES is focused mainly on peak positions because cross-section effects in the PES peak intensities are not taken into account here. 137 The DFT eigenvalues are shifted to align the HOMO peak with the corresponding IP, i.e. the total energy difference (ΔSCF) between the neutral and the cation, obtained with the same functional.…”

Metal–Organic Hybrid Interface States of A Ferromagnet/Organic Semiconductor Hybrid Junction as Basis For Engineering Spin Injection in Organic Spintronics

“…Using He I radiation (21.2 eV) enabled us to quickly investigate the development of the initial configuration of the DOS as a function of the OSC coverage at the FM‐OSC interface. On account of different photoionization cross‐sections for p‐orbitals of carbon and nitrogen and d‐orbitals of the metal atom26 and the additional use of He II radiation (40.8 eV) we can estimate the dominating elemental contribution in the experimental DOS.…”

“…Comparing the spin‐resolved total DOS from DFT‐GGA+U calculations at chemisorption geometry in the right parts of Figure 3 with the experimental data, we note a very good agreement. Observed intensity differences can be explained by the known elemental differences in the photoemission cross‐sections using He I radiation 26. Looking at the calculated DOS at the Fermi level itself, the character of the organic layer has changed from a semiconducting to a metallic behavior especially for FePc with a DOS peak for both spin directions which is cut at its maximum by E F .…”