Bulk sodium
===========

This example shows how to run a calculation on bulk sodium using either Quantum
ESPRESSO or PARACTED as starting mean-field codes.

In this example, we compute the RPA dielectric function and quasiparticle
energies for sodium.  We strongly recommand that you first run the silicon
example before running this example.  A couple of notes about the differences
between this and a semicondutor calculation:

1. Note that instead of using a k-grid shifted by a small q-vector  we use a
uniform, unshifted fine grid to represent the small q behavior in 03-wfn_fi.
This changes way that we calculate epsilon.  Note that in 07-epsilon we
calculate epsilon on a uniform grid but exclude the first small q point that is
given in a calculation  on a semiconductor (see silicon example).  The first
point in the qpoint list in 07-epsilon/epsilon.inp does NOT have the '1' flag
at the end.  In 07-epsilon_fine we calculate a single q point of size 1/gridsize
where  the gridsize is the linear dimension of the grid size specified in the
03-wfn_fi calculation.

2. For the calculation of Sigma, we link the epsmat file from 07-epsilon to
epsmat in the 08-sigma directory.  But now we link the epsmat file from
07-epsilon_fine to eps0mat in the 08-sigma directory.

3. The fine grid should be dense enough to adequately represent the intraband
transitions as well as the density of states.  If you plot the head of inverse
epsilon as a function of the small q-vector, you should see a parabolic
behavior which agrees very well with a Thomas-Fermi model of the system
calculated from the density  of states at the Fermi level.

4. Note that we cannot run the BSE codes on sodium because unusual case case of
a system in which some k-points have no occupied bands is not implemented.  We
could overcome this limitation by using a semicore pseudopotential for sodium
at the price of a higher computational cost.


To run this example, follow the steps below.  Remember to modify each script
before launching it!


1. Enter your mean-field directory of choice (ESPRESSO or PARATEC).
Read, customize and run/submit all scripts in that folder in the alphabetic order
they appear.


2. Go back to the directory containing this file, and modify/submit `script`.
Suggested 1 node (tested with ncpu = 32, walltime = 00:10:00).
We will:
- Generate dielectric matrix (directories 7)
- Calculate self-energy corrections (directory 8)
