CH3 molecule.

* Use of denchar + xcrysden (through an intermediate "Gaussian(TM)
  cube format")

Run Siesta on ch3_spin.fdf.
It will take a few iterations to relax the geometry. 

Then, run denchar on the same ch3_spin.fdf (it will only look at the
relevant keywords). It will produce a few ".cube" files.

Open any one of them with xcrysden and see the data grid information.
For example:

  xcrysden --g98_cube ch3.RHO.UP.cube

(VESTA and Molekel can also be used to display 'cube' files)

* Use of the .RHO output file + rho2xsf program (Andrei Postnikov's) +
  xcrysden.


After the Siesta run, you should find a ch3.RHO file in the
directory. It contains the charge density on the points of the
real-space grid.

We convert it to a format readable by Xcrysden using the "rho2xsf"
program by Andrei Postnikov. You can use it interactively, or through an
input file already prepared (xsf.input) :

rm -f ch3.XSF     # Make sure we remove any old files first
rho2xsf < xsf.input 

Now, open ch3.XSF with Xcrysden, and display the two datasets (spin up
and down charge, deformation charge, total potential) associated to
it. You can even combine the up (with factor +1.0) and down (with
factor -1.0) and see the spin density.

Make sure that the iso-value you choose is not to high, or the surface
will be inside the big C atom...

