[Pw_forum] shape of real space wave functions in wfc2kr

Jacopo Simoni simonij at tcd.ie
Wed Sep 27 00:51:59 CEST 2017


Dear PWSCF users,

I am trying to extract the real space wave functions that are computed from
the program wfc2kr.x

I have some questions:

1- why the number of k points (nks) is 1, even if I have in the restart
folder 8 k points ? the fact that in the code there is a cycle over nks
suggests that I can have more k points, I do not understand.

2- in my case dffts%nnr = dffts%nr1x * dffts%nr2x * dffts%nr3x, does this
mean that the total number of points in the real grid is equal to the total
number of points in the FFT grid ?
in particular I have nr1x=nr2x=nr3x=160, with nnr=4096000, while
npwx=256119. The total number of points nnr is considerably higher than the
number of plane waves, does this mean that the plane wave grid is
supplemented with 4096000-256119=3839881 zeros, am I right ?

3- the real space wave function evc_r(:,1) that I obtain in output from the
invfft routine can be reconstructed on the unit cell according to the
following index notation:
index = i + (j-1) * nr1x + (k-1) * nr2x * nr1x
r_ijk(:) = (i-1)/nr1x * a_1(:) + (j-1)/nr2x * a_2(:) + (k-1)/nr3x * a_3(:)
is this true or I am missing something ?

I really appreciate any help about these questions. Many thanks in advance.

Jacopo Simoni
Los Alamos National Laboratory, Theoretical division.
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