  Subsystem Density-Functional Theory (DFT) is an emerging technique for
calculating the electronic structure of complex molecular and condensed phase
systems. In this topical review, we focus on some recent advances in this field
related to the computation of condensed phase systems, their excited states,
and the evaluation of many-body interactions between the subsystems. As
subsystem DFT is in principle an exact theory, any advance in this field can
have a dual role. One is the possible applicability of a resulting method in
practical calculations. The other is the possibility of shedding light on some
quantum-mechanical phenomenon which is more easily treated by subdividing a
supersystem into subsystems. An example of the latter is many-body
interactions. In the discussion, we present some recent work from our research
group as well as some new results, casting them in the current state-of-the-art
in this review as comprehensively as possible.
