First Principles Calculation of Electronic Circular Dichroism Including Exciton Effects

Electronic circular dichroism (CD)—the differential absorption of left and right-hand circularly polarized light—is a powerful tool for identifying chiral molecules and probing chirality transfer at heterogeneous interfaces between molecules and crystalline materials. Time-dependent density functional theory (TD-DFT) is currently the most popular method for calculating CD, but its accuracy is limited by the choice of the exchange-correlation functional. In particular, it can be challenging to accurately describe systems with a mix of localized and delocalized states, such as those at a molecule-crystal interface, in TD-DFT. Ab initio many-body perturbation theory (MBPT) is an alternative approach that can describe optical excitations, including excitonic effects, in both molecules and crystals with great accuracy, but it is not yet widely applied to the study of electronic CD. Here, we demonstrate how to calculate electronic CD within the GW plus Bethe-Salpeter equation (GW-BSE) approach in MBPT through the application of Fermi’s Golden Rule. We then apply this approach to calculate the electronic CD of various chiral molecules.