title: Benchmarking Calculations of Excitonic Couplings between Bacteriochlorophylls.
abstract: Excitonic couplings between (bacterio)chlorophyll molecules are necessary for simulating energy transport in photosynthetic complexes. Many techniques for calculating the couplings are in use, from the simple (but inaccurate) point-dipole approximation to fully quantum-chemical methods. We compared several approximations to determine their range of applicability, noting that the propagation of experimental uncertainties poses a fundamental limit on the achievable accuracy. In particular, the uncertainty in crystallographic coordinates yields an uncertainty of about 20% in the calculated couplings. Because quantum-chemical corrections are smaller than 20% in most biologically relevant cases, their considerable computational cost is rarely justified. We therefore recommend the electrostatic TrEsp method across the entire range of molecular separations and orientations because its cost is minimal and it generally agrees with quantum-chemical calculations to better than the geometric uncertainty. Understanding these uncertainties can guard against striving for unrealistic precision; at the same time, detailed benchmarks can allow important qualitative questions-which do not depend on the precise values of the simulation parameters-to be addressed with greater confidence about the conclusions.
authors.affiliation: Centre for Engineered Quantum Systems, Centre for Quantum Computation and Communication Technology, and School of Mathematics and Physics, The University of Queensland , Brisbane QLD 4072, Australia.
authors.forename: Elise P
authors.initials: EP
authors.lastname: Kenny
authors.affiliation: Centre for Engineered Quantum Systems, Centre for Quantum Computation and Communication Technology, and School of Mathematics and Physics, The University of Queensland , Brisbane QLD 4072, Australia.
authors.forename: Ivan
authors.initials: I
authors.lastname: Kassal
mesh_terms: D001429:Bacteriochlorophylls / Q000737:chemistry*; D004735:Energy Transfer; D008958:Models, Molecular; D011789:Quantum Theory; D055672:Static Electricity
chemical_list: D001429:Bacteriochlorophylls