Description of the procedure to be used to do LDA+U Calculation.

This feature is available only in PAW. The LDA+U framework is described in
the paper [1].
Two choice of double counting are provided: the Full Localized limit (cf [1])
and the Around Mean Field approximation (cf [2]).
Our implementation is described in [3].
It follows the main lines of the paper [4].
For details on keywords, see keyword usepawu in input variables.

In both the output and log files, we can find:
- The LDA+U contribution of energy is contained inside the PAW Spherical terms.
- The Decomposition of the LDA+U energy is given (Interaction energy, Double
  counting term, and sum of the two). 
- The orbital density matrix (n_{m,m'}^{\sigma}), also called occupation
  matrix (corresponding to eq 9 of ref [4]  and eq 1 of ref [1]) is also
  given for each atom.

Consistency between total energy and forces in LDA+U have been checked.

The reader can find an example in the directory Test_v5 (t08.in)

[1] A. Lichtenstein et al PRB 52, 5467 (1995)
[2] M. T. Czyzyk and  G. A. Sawatzky PRB 49, 14211 (1994)
[3] B. Amadon, F. Jollet and M. Torrent (in preparation (and suggested acknowledgment))
[4] O. Bengone et al PRB 62, 16392 (2000)

