Large-scale many-body perturbation theory calculations on leadership class facilities*

Many-body perturbation theory (MBPT) has been shown to provide an accurate description of excited state properties for the simulation of spectroscopic signatures of materials and molecules. The advent of exascale computing offers the appealing opportunity to expand the applicability of MBPT methods to systems of unprecedented size and complexity, e.g. to thousands of electrons. We will discuss methodological advances implemented in the WEST code [http://west-code.org] for both GW and BSE calculations. We will present new functionalities enabled by the concurrent use of WEST and the Qbox code [http://qboxcode.org], with focus on interoperability paradigms. We will discuss the advantages of developing interoperable software, and we will present results for the calculation of spectroscopic properties of defective insulators and semiconductors hosting optically addressable spin-defects.