Electronic Excitations from GW-BSE in Large Molecular Systems via hybrid embeddings

Many-Body Green’s Functions Theory in the GW approximation with the Bethe-Salpeter Equation (GW-BSE) is a post Density-functional theory method to obtain accurate energies of charged and neutral electronic excitations for a wide range of materials from inorganic crystals to organic molecules. However, as GW-BSE scales, depending on implementation details, with the fourth power of the system size, its application to large complex molecular systems, such as polymers, polymer composites, or complex supramolecular assemblies is challenging.

In this talk we showcase some computational strategies based on embedding an active GW-BSE subregion of a complex system in regions described by low level methods as implemented in our VOTCA-XTP package¹. We focus particularly on embedding a GW-BSE model withing a projector based splitting of DFT densities. We consider the effects of eg. basis-set truncations and restrictions to product space basis on the calculated excitations of a few prototypical systems such as solvated dyes.

1. G. Tirimbò, V. Sundaram, O. Çaylak, W. Scharpach, J. Sijen, C. Junghans, J. Brown, F. Zapata Ruiz, N. Renaud, J. Wehner, and B. Baumeier, "Excited-state electronic structure of molecules using many-body Green’s functions: Quasiparticles and electron–hole excitations with VOTCA-XTP", J. Chem. Phys. 152, 114103 (2020) https://doi.org/10.1063/1.5144277