  We introduce the unification of dynamical mean field theory (DMFT) and
linear-scaling density functional theory (DFT), as recently implemented in
ONETEP, a linear-scaling DFT package, and TOSCAM, a DMFT toolbox. This code can
account for strongly correlated electronic behavior while simultaneously
including the effects of the environment, making it ideally suited for studying
complex and heterogeneous systems containing transition metals and lanthanides,
such as metalloproteins. We systematically introduce the necessary formalism,
which must account for the non-orthogonal basis set used by ONETEP. In order to
demonstrate the capabilities of this code, we apply it to carbon
monoxide-ligated iron porphyrin and explore the distinctly quantum-mechanical
character of the iron $3d$ electrons during the process of photodissociation.
