quantum-espresso

History

Paolo Giannozzi 6148f5e5c5 Obscure line present in all examples replaced with a much simpler one. See https://stackoverflow.com/questions/50148175/what-does-cd-echo-0-sed-s-1-do-in-bash-script Note: some trailing blanks have been removed as well by the script I used. Use "git diff -b" to see only the true changes.		2022-09-03 11:53:33 +02:00
..
reference	Calculate vdW kernel on the fly: fourth commit	2019-09-23 14:50:52 -04:00
reference_dscf	Calculate vdW kernel on the fly: fourth commit	2019-09-23 14:50:52 -04:00
README	Calculate vdW kernel on the fly: fourth commit	2019-09-23 14:50:52 -04:00
run_example	Obscure line present in all examples replaced with a much simpler one.	2022-09-03 11:53:33 +02:00
run_example_delta_scf	Obscure line present in all examples replaced with a much simpler one.	2022-09-03 11:53:33 +02:00

README

This example shows how to use the vdw-DF functional in pw.x. It
calculates the non-local correlation contribution to the energy and
potential according to

   M. Dion, H. Rydberg, E. Schroeder, D.C. Langreth, and
   B.I. Lundqvist, Phys. Rev. Lett. 92, 246401 (2004).

henceforth referred to as DION. Further information about the
functional and its corresponding potential can be found in:

   T. Thonhauser, V.R. Cooper, S. Li, A. Puzder, P. Hyldgaard,
   and D.C. Langreth, Phys. Rev. B 76, 125112 (2007).

The proper spin extension of vdW-DF, i.e. svdW-DF, is derived in

   T. Thonhauser, S. Zuluaga, C.A. Arter, K. Berland, E. Schroder,
   and P. Hyldgaard, Phys. Rev. Lett. 115, 136402 (2015).

henceforth referred to as THONHAUSER.


Two review articles show many of the vdW-DF applications:

   D.C. Langreth et al., J. Phys.: Condens. Matter 21, 084203 (2009).

   K. Berland et al., Rep. Prog. Phys. 78, 066501 (2015).


The method implemented is based on the method of G. Roman-Perez and
J.M. Soler described in:

   G. Roman-Perez and J.M. Soler, Phys. Rev. Lett. 103, 096102 (2009).

henceforth referred to as SOLER.


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The example will first check if all the necessary files are present, and
then run the simulations. After the check, the example will proceed with
two simulations, in particular

1) A variable cell relaxation of a simple 1x1 graphite. The parameters
used (such as k-point mesh and energy cutoffs) are not converged, use them
only for test runs, increase them accordingly for production runs.
Here the stress will be used to converge the cell at 0 pressure.

2) A self-consistent energy calculation of a water dimer in the
equilibrium configuration.  Check the energies and forces against
those in the reference file.

bonus) If you have the Ar.pz-rrkj.UPF in the PP_dir, you can activate the
last example by removing the comments from the execution lines (277-280).
In this example it is shown how to run a BFGS relaxation of the forces 
for the Argon dimer. Check that the energies and forces agree with those
in the reference file, and that the final positions are correct.