  We introduce a spectral density functional theory which can be used to
compute energetics and spectra of real strongly--correlated materials using
methods, algorithms and computer programs of the electronic structure theory of
solids. The approach considers the total free energy of a system as a
functional of a local electronic Green function which is probed in the region
of interest. Since we have a variety of notions of locality in our formulation,
our method is manifestly basis--set dependent. However, it produces the exact
total energy and local excitational spectrum provided that the exact functional
is extremized. The self--energy of the theory appears as an auxiliary mass
operator similar to the introduction of the ground--state Kohn--Sham potential
in density functional theory. It is automatically short--ranged in the same
region of Hilbert space which defines the local Green function. We exploit this
property to find good approximations to the functional. For example, if
electronic self--energy is known to be local in some portion of Hilbert space,
a good approximation to the functional is provided by the corresponding local
dynamical mean--field theory. A simplified implementation of the theory is
described based on the linear muffin--tin orbital method widely used in
electronic strucure calculations. We demonstrate the power of the approach on
the long--standing problem of the anomalous volume expansion of metallic
plutonium.
