This exercise illustrates the use of different functionals and
spin polarization.


The system in which we will work is bulk Fe.
This is a difficult system, for many reasons.
First, it needs core corrections for a proper description
of the magnetism. Second, the results depend a lot
on the functional used.
Third, since the d-orbitals are very compact, and
core corrections are present, a large meshcutoff is
necessary for proper convergence. Finally, metallic
character with a large density of states at the Fermi level
makes it necessary to use a fine k-point sampling.
The input files have been built to take into account
these stringent conditions.

There are two subdirectories with BCC and FFC Fe.
In each of this directories there are four directories
with the same input except the functional : LDA
GGA and spin polarized LDA and GGA.
We are going to study how the bulk parameters 
(lattice constant, bulk modulus) depend on the
functional used. So in each subdirectory run make
and a graph showing the FreeEnergy (the electronic
temperature is quite high)  vs. cell volume
will be plot. The data will be adjusted to a murnaghan
equation of state and the bulk modulus will appear
on the graph, while the lattice constant will be an output
in the terminal. Each graph will be saved in a *.png file.

You can plot all the graphs together executing:

in this directory. 

Answer these questions:
Which is the most stable phase of Fe?
How does the magnetic moment vary with each functional?

There is a paper with the corresponding results obtained
using a PW basis set in this directory. The main differences
are due to the fact that the basis set isn't really well
optimized. 
