Serenity: A subsystem quantum chemistry program

We present the new quantum chemistry program Serenity. It implements a wide variety of functionalities with a focus on subsystem methodology. The modular code structure in combination with publicly available external tools and particular design concepts ensures extensibility and robustness with a focus on the needs of a subsystem program. Several important features of the program are exemplified with sample calculations with subsystem density‐functional theory, potential reconstruction techniques, a projection‐based embedding approach and combinations thereof with geometry optimization, semi‐numerical frequency calculations and linear‐response time‐dependent density‐functional theory. © 2018 Wiley Periodicals, Inc. The authors present a new quantum chemistry library/program, Serenity, which is focused on subsystem methods. A variety of features are demonstrated, highlighting the advantages of modular code for the development of new embedding methods and adaptations of known theories within the subsystem framework. These features include but are not limited to subsystem density‐functional calculations including analytical gradients as well as linear‐response time‐dependent DFT calculations for embedded systems.