quantum-espresso/PP/examples/example05

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.