VASP SrVO3 Density of states
------------------------------
Here we compute the density-of-states using VASP. 

Total Density-of-states
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

INPUT: :download:`INCAR` | :download:`KPOINTS` | :download:`POTCAR` | :download:`POSCAR`      

OUTPUT: :download:`CONTCAR` | :download:`OSZICAR`  | :download:`OUTCAR`  | :download:`DOSCAR` | :download:`PROCAR` | :download:`vasp.out` 

This calculation
needs to be a static run (ie. no structural relaxation NSW=0). 
Please see  :ref:`relaxation introduction <vaspintro>` for a basic description of the four required files.
A typical INCAR would be as follows:

.. code-block:: bash

  ISPIN = 2             # Spin polarized calculation
  MAGMOM= 0  4  0 0 0   # Initialization of moments
  PREC = med            # Sets cutoffs and grids
  NSW=0                 # Don't move the atoms
  ISMEAR = -5           # Use the tetrahedron method
  ENCUT=375             # Plane wave cuttoff
  NEDOS=5000            # Number of energy points for DOS

This would produce a file called DOSCAR which has the total density
of states and the projected DOS if requested. The format of the DOSCAR
is as follows:

.. code-block:: bash

   5   5   0   0 # first five lines not terribly useful...
  0.1148420E+02  0.3857953E-09  0.3857953E-09  0.3857953E-09  0.5000000E-15
  1.000000000000000E-004
  CAR 
 unknown system                          
     12.00000000  -3.00000000 5000  4.96643483  1.00000000  # Total_elec unknown NEDOS Efermi unknown
     -3.000  0.0000E+00  0.0000E+00  0.7000E+01  0.7000E+01 # Energy tdos_up tdos_dn cdos_up cdos_dn 
     -2.997  0.0000E+00  0.0000E+00  0.7000E+01  0.7000E+01 # ...
     -2.994  0.0000E+00  0.0000E+00  0.7000E+01  0.7000E+01 # ...
     ...

One problem you will have is that VASP defaults to making the mim/max energy of
the DOS as the entire range of the spectrum which you rarely care about. If you
use many points (ie. NEDOS) you will still resolve things at the expense of
huge files. The best answer is to finish writing our own software to compute
the DOS as a postprocessing step. In the meantime, one can just keep the
WAVECAR and quickly rerun to recompute the DOS in a smaller energy range.  Do a
quick plot of the DOS to find out what max/min energy you want. Be careful that
the plotting code does not shift the results by the Fermi energy. You can
extract the total DOS from the DOSCAR file using a very antiquated script
called dformat.py and then plot it however you like. dformat.py desperately
needs to be rewritten:

.. code-block:: bash

  $ dformat.py total noshiftfermi > dos.out 

Now you can add these two lines to the 
INCAR and rerun:

.. code-block:: bash

  EMIN=-3               # Minimum energy for computing DOS
  EMAX=12               # Maximum energy for computing DOS



.. figure:: srvo3_dos.png
  :scale: 60%

  **DOS**. This is the density of states for SrVO3. I only plotted one 
  spin component as the calculaion found a non-spin-polarized solution.
  :download:`EPS <srvo3_dos.eps>`
  :download:`Plotting Script <plot_dos.py>`

Partial Density-of-states
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If you want to have the projected DOS, you need to set the LORBIT parameter
in the INCAR. You should probably be in the habbit of turning this on.

.. code-block:: bash

  LORBIT=11             # Compute projections along with phase factors

This will result in the creation of the PROCAR file which has the projections
onto local orbitals for each k-point and each band. We will not worry about the
PROCAR at this point.