Chapter 3 - From Atomistic Modeling to Electronic Properties of Light-Harvesting Systems

Abstract

Plants and certain bacteria use photosynthesis as their main source of energy. The primary step of photosynthesis is the harvesting of sun light. For several light-harvesting complexes, crystal structures have been resolved by now. This allows for an atomic-level modeling of the structures, and henceforth, one can aim at understanding the structure–function relationship. Due to the size of the light-harvesting complexes on the one hand and the influence of electronic effects on the other hand, a multiscale modeling approach is needed to obtain the connection between the atomic structure and the excitation transfer in these biological entities. Based on such a model, optical properties can be determined as well. The multiscale calculations constitute a time-dependent combination of molecular dynamics simulations and quantum chemistry methods. This procedure results in a time-dependent Hamiltonian that subsequently is employed either in ensemble-averaged wave packet simulations or via the spectral density in density matrix calculations. Furthermore, the combination of molecular dynamics simulations and quantum chemistry can be employed to investigate the question of spatially correlated fluctuations in light-harvesting complexes.