Large-scale first principles calculations with leadership class HPC using many-body perturbation theory

Predictive modeling of excited state properties typically employs Green's function based many-body perturbation theory (MBPT) methods. Pre-exascale machines offer the opportunity to expand the science domain of such methods to systems of unprecedented size, accounting for the realistic complexity of e.g. nanostructured, interfaced, disordered, and defective materials. In this talk we discuss how methodological advances coded in WEST [www.west-code.org] provide an efficient formulation of electron-electron, electron-phonon and electron-hole interactions, that is applied to systems with thousands of electrons. We will discuss the advantages of the algorithms used in WEST over standard techniques, its parallel performance on leadership class HPC machines, and provide results for the calculation of spectroscopic features of liquids and defective solids. We will discuss the inclusion of electron-phonon coupling effects to simulate photoelectron spectra and carrier lifetimes of carbon-based nanoparticles. Finally, we will present the new functionalities enabled by the concurrent use of WEST and the Qbox code [qboxcode.org], with focus on the interoperability paradigm that the coupling advocates. Work in collaboration with: A. Gaiduk, G. Galli, M. Gerosa, F. Gygi, I. Hamada, C. Knight, H. Ma, R. McAvoy, N.L. Nguyen, H. Yang, H. Seo, H. Zheng.