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O: Fachverband Oberflächenphysik

O 82: Poster Session VI: Poster to Mini-Symposium: Frontiers of electronic-structure theory III

O 82.5: Poster

Wednesday, March 3, 2021, 13:30–15:30, P

Assessment of the Ab Initio Bethe-Salpeter Equation Approach for the Low-Lying Excitation Energies of Bacteriochlorophylls and Chlorophylls — •Zohreh Hashemi¹ and Linn Leppert^1,2 — ¹Institute of Physics, University of Bayreuth, Germany — ²MESA+ Institute for Nanotechnology, University of Twente, Netherlands

Bacteriochlorophyll and Chlorophyll molecules are crucial building blocks of the photosynthetic apparatus in bacteria, algae and plants. In this contribution we assess the accuracy of ab initio many body perturbation theory within the GW approximation and Bethe-Salpeter equation (BSE) approach for calculating the electronic structure and optical excitations of seven members of this important family of light harvesting pigments. We compare our calculations with results from time-dependent density functional theory, multireference RASPT2 and experimental literature results. We find that optical excitations calculated with GW+BSE are in excellent agreement with experimental data, with an average deviation of less than 100 meV for the first three bright excitations of the entire family of (Bacterio)chlorophylls. Contrary to state-of-the-art TDDFT with an optimally-tuned range-separated hybrid functional, this accuracy is achieved in a parameter-free approach. Moreover, GW+BSE predicts the energy differences between the low-energy excitations correctly, and eliminates spurious charge transfer states that TDDFT with (semi)local approximations is known to produce.