Multiscale polarizable embedding of quasiparticle and electron-hole excitations from many-body Green’s functions (GW-BSE) with VOTCA-XTP

We present the open-source VOTCA-XTP software [1] for the calculation of the excited-state electronic structure of molecules using many-body Green’s functions theory in the GW approximation with the Bethe–Salpeter Equation (BSE). Its implementation is based on Gaussian orbitals, including, i .a., resolution-of-identity techniques, different methods for the frequency integration of the self-energy, acceleration with a hybrid OpenMP/Cuda scheme, or inclusion of a classical polarizable environment in a coupled quantum- and molecular-mechanics (QM/MM) scheme. Two showcase examples are discussed: First, a multiscale simulation framework for quantitative predictions of the high-energy part of ultraviolet photoelectron spectroscopy (UPS) spectra of amorphous molecular solids [2]. Second, we investigate the intermolecular charge-transfer excited states in morphologies of low-donor content rubrene-C60 mixtures using different variants of GW-BSE/MM setup.
[1] 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)
[2] Quantitative Predictions of Photoelectron Spectra in Amorphous Molecular Solids from Multiscale Quasiparticle Embedding, Phys. Rev. B 101, 035402 (2020)