Massively parallel fragment-based quantum chemistry for large molecular systems: the SERESTIPY software

We present the SERESTIPY software as an add-on to the quantum-chemistry program SERENITY. SERESTIPY is a representational-state transfer-oriented application programming interface written in the Python programming language enabling parallel subsystem density-functional theory calculations. We introduce approximate strategies in the context of frozen density embedding time-dependent density-functional theory to make parallel large-scale excited-state calculations feasible. Their accuracy is carefully benchmarked with calculations for a model system consisting of porphine rings. We apply this framework to a nanotube made up of those porphine rings consisting of 12160 atoms (or 264 960 basis functions) and obtain its electronic structure and absorption spectrum in less than a day of computational time.