Subsystem Density-Functional Theory (Update)

This is the authors' abstract. We don't add key points for this paper.

The past years since the publication of our review on subsystem density-functional theory (sDFT) [WIREs Comput. Mol. Sci. 2014, 4:325--362] have witnessed a rapid development and diversification of quantum mechanical fragmentation and embedding approaches related to sDFT and frozen-density embedding (FDE). In this follow-up article, we provide an update addressing formal and algorithmic work on FDE/sDFT, novel approximations developed for treating the non-additive kinetic energy in these DFT/DFT hybrid methods, new areas of application and extensions to properties previously not accessible, projection-based techniques as an alternative to solely density-based embedding, progress in wavefunction-in-DFT embedding, new fragmentation strategies in the context of DFT which are technically or conceptually similar to sDFT, and the blurring boundary between advanced DFT/MM and approximate DFT/DFT embedding methods.