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VOTCA_Software_for_Electronically_Excited_States.pdf (1.14 MB)

Excited-State Electronic Structure of Molecules Using Many-Body Green's Functions: Quasiparticles and Electron-Hole Excitations with VOTCA-XTP

preprint
submitted on 30.12.2019, 19:44 and posted on 31.12.2019, 21:10 by Gianluca Tirimbò, Vivek Sundaram, Onur Çaylak, Wouter Scharpach, Javier Sijen, Christoph Junghans, Joshua Brown, Felipe Zapata Ruiz, Nicolas Renaud, Jens Wehner, Björn Baumeier
We present the open-source VOTCA-XTP software 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). This work provides a summary of the underlying theory and discusses details of its implementation based on Gaussian orbitals, including, i.a., resolution-of-identity techniques, different approaches to the frequency integration of the self-energy or acceleration by offloading compute-intensive matrix operations using GPUs in a hybrid OpenMP/Cuda scheme. A distinctive feature of VOTCA-XTP is the capability to couple the calculation of electronic excitations to a classical polarizable environment on atomistic level in a coupled quantum- and molecular-mechanics (QM/MM) scheme, where a complex morphology can be imported from Molecular Dynamics simulations. The capabilities and limitations of the GW -BSE implementation are illustrated with two examples. First, we study the dependence of optically active electron-hole excitations in a series of diketopyrrolopyrrole-based oligomers on molecular-architecture modifications and the number of repeat units. Second, we use the GW -BSE/MM setup to investigate the effect of polarization on localized and intermolecular charge-transfer excited states in morphologies of low-donor content rubrene-fullerene mixtures. These showcases demonstrate that our implementation currently allows to treat systems with up to 2500 basis functions on regular shared-memory workstations, providing accurate descriptions of quasiparticle and coupled electron-hole excited states of various character on an equal footing.

Funding

Innovational Research Incentives Scheme Vidi of the Netherlands Organisation for Scientific Research (NWO) with project number 723.016.002

NWO and the Netherlands eScience Center through project number 027.017.G15, within the Joint CSER and eScience program for Energy Research (JCER 2017)

History

Email Address of Submitting Author

b.baumeier@tue.nl

Institution

Eindhoven University of Technology

Country

The Netherlands

ORCID For Submitting Author

0000-0002-6077-0467

Declaration of Conflict of Interest

None.

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