Self-interaction correction, electrostatic, and structural influences on time-dependent density functional theory excitations of bacteriochlorophylls from the light-harvesting complex 2

• Published in: The Journal of chemical physics 2020-10, Vol.153 (14), p.144114-144114
• Main Authors: Kehrer, Juliana, Richter, Rian, Foerster, Johannes M., Schelter, Ingo, Kümmel, Stephan
• Format: Article
• Language: English
• Subjects: Bacteriochlorophylls - chemistry; Beijerinckiaceae - enzymology; Charge transfer; Chromophores; Computational efficiency; Coupling (molecular); Crystal structure; Crystallography; Density Functional Theory; Excitation; First principles; Light-Harvesting Protein Complexes - chemistry; Mathematical analysis; Models, Chemical; Molecular Conformation; Molecular dynamics; Molecular Dynamics Simulation; Static Electricity; Time dependence
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/5.0014938

First-principles calculations offer the chance to obtain a microscopic understanding of light-harvesting processes. Time-dependent density functional theory can have the computational efficiency to allow for such calculations. However, the (semi-)local exchange-correlation approximations that are computationally most efficient fail to describe charge-transfer excitations reliably. We here investigate whether the inexpensive average density self-interaction correction (ADSIC) remedies the problem. For the systems that we study, ADSIC is even more prone to the charge-transfer problem than the local density approximation. We further explore the recently reported finding that the electrostatic potential associated with the chromophores’ protein environment in the light-harvesting complex 2 beneficially shifts spurious excitations. We find a great sensitivity on the chromophores’ atomistic structure in this problem. Geometries obtained from classical molecular dynamics are more strongly affected by the spurious charge-transfer problem than the ones obtained from crystallography or density functional theory. For crystal structure geometries and density-functional theory optimized ones, our calculations confirm that the electrostatic potential shifts the spurious excitations out of the energetic range that is most relevant for electronic coupling.