[Pw_forum] nqx=1 in input but full grid in output

[Roberto Gaspari]

Dear all,

I am performing my first hybrid functional calculations with PWSCF.
I was trying to simulate a quite large system (24 at/unit cell  volume=2082.0010 a.u.^3)
on a large machine (CINECA-Fermi). The scf appears quite slow so I was trying to test the convergence of the grid density for the Fock operator, to see if I can be any faster without losing too much accuracy.
Following the EXX examples I set in the &system section

&system
  ................
   ecutwfc = 70,
   ecutrho = 280,
   occupations = 'smearing',
   degauss = 0.01,
   input_dft='pbe0', nqx1 = 1, nqx2 = 1, nqx3 = 1,
 /

and for the regular Monkhorst-Pack grid:

/
K_POINTS (automatic)
3 3 3 1 1 1


In the output file I obtain a Monkhorst-Pack of 42 k-points, which is fine.
Anyway I was expecting to get something like

EXX: grid of k+q point setup nkqs =         1

since, as far as I have understood, setting all nqxs to 1 amounts to performing a q=0 calculation

I get, instead:

EXX: grid of k+q point setup nkqs =         42

that is the grid for the Fock operator is as dense as the regular Monkhorst-Pack grid.

Does all this correspond to an expected behavior of pwscf?

I thank all of you for your attention,

Best Regards,

Roberto Gaspari,
Italian Institute of Technology,
Concept Lab

















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