To have 'better' projector in LDA+U calculations some localized Wannier functions of
the relevant bands around the Fermi energy can be used. See for instance N.Marzari
and D.Vanderbilt, PRB 56, 12847 (1997) and I. Sousa, N. Marzari, and
D.Vanderbilt, PRB 65, 035109 (2001) for the definition and construction
of Maximally Localized Wannier Functions (MLWF).

Although it is possible to generate MLWF with the software distributed by
Nicola Marzari at www.wannier.org, here we follow a simpler prescription
and fix the phase-factor freedom---intrinsic in any Wannier function
determination---in a sub-optimal but simple way using the atomic
wavefunction as a guide.

This is done as a post-processing step with a poormanwannier tool (pmw.x)
that reads atomic wavefunctions and band structure of an LDA calculation
and replaces the atomic wavefunctions with our simple Wannier functions.

The subsequent LDA+U calculation is performed specifying in the system
namelist U_projection_type='file' so that the freshly produced Wannier
functions are used in the projection.
The outcome of this calculation is an insulating state with d-level
occupations really close to 0 or 1.

In addition to this, the example shows how to obtain fat bands (i.e., band
structures "weighted" by the overlap with atomic wave functions) and thereby
identify which bands have the largest content of, e.g., Fe 3d-character.
A non-self consistent calculation is used to compute the band structure along
a path in the Brillouin zone, followed by the calculation of the projections
onto atomic orbitals (projwfc.x) and the band symmetry analysis (bands.x).
The small utility plotband.x combines those data and produces band structure
plots with an additional third column containing the weight on the selected
wavefunction (or the sum, if more than one is specified). In this case, the
projections onto the 10 atomic 3d wavefunctions of the two Fe are summed up.