[Pw_forum] start_q, last_q, start_irr, last_irr

[Jeffrey Mullen]

Dear Elie,

If I understand you correctly, you want to run a series of separate 
calculations, one for each q in which you are interested.  You can 
perform the calculations for one phonon per input file by setting 
ldisp=.false. and defining the q you need at the bottom of the file.

For example

title line
&inputph
     tr2_ph=1.0d-12,
    prefix='gr',
    amass(1)=12.01070,
     .
     .
     .
    ldisp=.false.
  /
0.0000000 0.0000000 0.0000000 <---- q_x    q_y   q_z

Here I have left out any other variable definitions like thresholds etc. 
You can then run 10, 20, 30 or however many phonons you need to make 
your dispersion curve. In this way, you should not need start_q, etc.

Cheers
Jeff Mullen
North Carolina State University




On 6/1/10 4:47 PM, Elie Moujaes wrote:
> Dear all,
>
> I am trying to get the phonon dispersion of graphene by taking each q 
> on its own and performing the necessary operations (i.e using start_q, 
> last_q, start_irr, last_irr) then merging the points all together . 
> Can anyone please explain to me more about these parameters. I read 
> the INPUT_PH and the examples in GRID but did not actually understand 
> what these mean..I got that irr is irreducible representation but how 
> can one set these each time one runs the calculation for a q.
>
> Thanks ina dvance
>
> Elie Moujaes
> University of nottingham
> NG7 2RD
> Nottingham
>
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