quantum-espresso/PHonon/examples/GRID_example

This example shows how to use ph.x on a GRID. The GRID phonon parallelization
allows to split a phonon calculation into relatively small jobs, each
runing a subset of linear-response calculations for a small number of
wave-vectors or irreps or combinations. The jobs can then be run
independently and the final results collected. Documentation is available
here: "Calculation of Phonon Dispersions on the GRID using Quantum ESPRESSO",
R. di Meo, A. Dal Corso, P. Giannozzi, and S. Cozzini, in
"Chemistry and Material Science Applications on Grid Infrastructures", Editors:
S. Cozzini, A. Lagana', ICTP Lecture Notes Series, Vol.24, pp.165-183 (2009)
http://users.ictp.it/~pub_off/lectures/lns024/10-giannozzi/10-giannozzi.pdf

The calculation is the same as example06. In run_example all q-vectors and
all irreps are split into different runs. In run_example_1 all q-vectors are 
split into different runs.

The calculation in run_example proceeds as follows:

1) A self consistent calculation is done:
(input alas.scf.in, output alas.scf.out)

2) A preparatory phonon run with start_irr=0, last_irr=0 calculates the
displacement patterns:
(input alas.ph.in0, output alas.ph.out0)

3) ph.x is run for each representation of each q point. 
The code runs with different outdir and only the xml files are copied 
in the same outdir
(input input.#q.#irr, output output.#q.#irr)

4) A final phonon calculation collects all the dynamical matrices
 (input alas.ph.in, output alas.ph.out)

5) q2r and matdyn compute the interatomic force constants and the dispersions.

The calculation in run_example_1 proceeds as follows:

1) A self consistent calculation is done:
(input alas.scf.in, output alas.scf.out)

2) ph.x is run for each q point. 
The code runs with different outdir. This step can be done in different
machines or different processors. 
(input input.#q, output output.#q)

3) q2r and matdyn compute the interatomic force constants and the dispersions.

The calculation in run_example_3 is a variation of run_example
in which all the bands are calculated first and then the band files are
copied in the outdir directories or each ph.x run.
At variance with run_example it does not recalculate the
initialization (bands and electric field) for each irreducible 
representation. Each different q must be run in a different directory 
using lqdir=.true. 
Note that the script runs in a different outdir directory for each q and irrep.
This simulates the use of separate machines, but if you run on many CPUs
that share the same disk you can avoid copying the files using the same 
outdir directory for all q and irrep. 

The run is as follows:

1) A self consistent calculation is done:
(input alas.scf.in, output alas.scf.out)

2) A preparatory phonon run with lqdir=.true. and only_wfc=.true. calculates 
the displacement patterns and the bands.
(input alas.ph.wfc.in, output alas.ph.wfc.out)
Note that the scf calculation and this band calculation can be done
with the option twfcollect=.true. (that needs to be set only in the pw.x
input) with a number of processors different from the following phonon run.

3) The dielectric constant, effective charges and the part of the dynamical
matrix not dependent on the perturbation can be calculated in a
second initialization run using lqdir=.true. and only_init=.true..
This step can be skipped but in this case all representations corresponding
to q=0 will calculate the electric field part.
(input alas.ph.in0, output alas.ph.out0)

3-5) The rest is as in run_example (Note however that lqdir=.true. must
be used in all phonon inputs).