[Pw_forum] Re: q not allowed (Katalin Gaal-Nagy)

[Katalin Gaal-Nagy]

Dear Eyvaz,

thanks for the reply.

I know that it was explained before, and I generated the q points exactly 
in that way: Running pw.x for some minutes (the q points have the correct 
units, etc, thanks Cesar for the hint!), take the q points and put them 
to the phonon calculation. It worked well with the 4x4x4 mesh.
For the 4x4x8 mesh I did the same, compared the two grids and calculated 
just the q points which have been missing. And there the error appeared 
for some (not all) of the new q points.

For curiosity, I just removed the not-allowed q points from the files, but 
then there are some q points missing. At the moment I guess that due to 
some symmetry operation some signs of the q points are changed, or, 
translated to other IBZs, whatever, and I want to look through the q2r 
routine and print out the "reference" q points and compare them with the q 
points I have in the files with the dynamical matrices. Then I will see 
what is going on. (I still use the "old" version of the q2r).

Unfortunatly, I am not at the office for one week, but I will give a short 
report as soon as I have some news.

All the best,
Katalin


> Hi,
>
> Sorry interfering in, but it was explained before why
> this happens. Let me remind again.
>
> In my opinion, there is two solutions of the problem:
>
> 1) use >v3.0 where you can directly put  nq1, nq2, nq3
> and everything will go smoothly:
> (something like this:)
> &inputph
>  tr2_ph=1.0d-14,
>  prefix='C8',
>  ldisp=.true.,
>  nq1=4, nq2=4, nq3=4
>  amass(1)=12.01,
>  outdir='$TMP_DIR/',
>  fildyn='C8.dyn',
> /
>
> In this case you have to supply enough CPU time to
> complete dynamical matrix calculations. Otherwise in
> some clusters you will lose your temporary files and I
> am not sure that an option "recover" will help in this
> case. I would be happy if this one is not true. In
> fact, I faced this problem.
>
> 2) If you prefer say 2.1 version, again, it was
> explained before, and the best way is to generate
> q-points via pw.x (kill the job in few seconds and
> look at *.scf.out file) and put them into your input
> file.
> In this case the \Gamma point is calculated separately
> and, thus, remove the \Gamma point from the list.
>
> Hope they are helpful.
>
> Bests,
> Eyvaz.
>
> --- cesards at msi.umn.edu wrote:
>
>> A common cause for this problem is defining q-points
>> in reciprocal cell
>> coordinates. q-points must be defined in 2pi/a
>> ccoordinates.
>>
>> Yours,
>>
>> Cesar R.S. da Silva
>>
>>