We use real-time density functional theory on a real-space grid to calculate electronic excitations of bacteriochlorophyll chromophores of the light-harvesting complex 2 (LH2). Comparison with Gaussian basis set calculations allows us to assess the numerical trust range for computing electron dynamics in coupled chromophores with both types of techniques. Tuned range-separated hybrid calculations for one bacteriochlorophyll as well as two coupled ones are used as a reference against which we compare results from the adiabatic time-dependent local density approximation (TDLDA). The tuned range-separated hybrid calculations lead to a qualitatively correct description of the electronic excitations and couplings. They allow us to identify spurious charge-transfer excitations that are obtained with the TDLDA. When we take into account the environment that the LH2 protein complex forms for the bacteriochlorophylls, we find that it substantially shifts the energy of the spurious charge-transfer excitations, restoring a qualitatively correct electronic coupling of the dominant excitations also for TDLDA.

Centro de Ciencias Naturais e Humanas Federal University of ABC Santo Andre Brazil

Computational Biochemistry University of Bayreuth Bayreuth Germany

Institute of Molecular Cell and Systems Biology University of Glasgow Glasgow United Kingdom

Laboratory of Anoxygenic Phototrophs CZ 379 01 Trebon Czech Republic

Theoretical Physics 4 and Computational Biochemistry University of Bayreuth Bayreuth Germany

Theoretical Physics 4 University of Bayreuth Bayreuth Germany

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