  We develop a cluster dynamical mean field theory of the periodic Anderson
model in three dimensions, taking a cluster of two sites as a basic reference
frame. The mean field theory displays the basic features of the Doniach phase
diagram: a paramagnetic Fermi liquid state, an antiferromagnetic state and a
transition between them.
  In contrast with spin density wave theories, the transition is accompanied by
a large increase of the effective mass everywhere on the Fermi surface and a
substantial change of the Fermi surface shape across the transition. To
understand the nature and the origin of the phases near the transition, we
investigate the paramagnetic solution underlying the antiferromagnetic state,
and identify the transition as a point where the $f$ electrons decouple from
the conduction electrons undergoing an orbitally selective Mott transition.
This point turns out to be intimately related to the two impurity Kondo model
quantum critical point. In this regime, non local correlations become important
and result in significant changes in the photoemission spectra and the de
Haas-van Alphen frequencies. The transition involves considerable $f$ spectral
weight transfer from the Fermi level to its immediate vicinity, rather than to
the Hubbard bands as in single site DMFT.
