[Pw_forum] Plotting phonon dispersion

Lorenzo Paulatto paulatz at gmail.com
Mon Feb 19 20:41:39 CET 2018

On 02/19/2018 07:27 PM, elchatz at auth.gr wrote:
> in the scf. It's good to know if this is more possible to work as ph.x
> takes about 4 days.

No point in doing all the calculation again.. just use the coordinates 
of the points for god's sake. With ibrav=4, Gamma is 0,0,0, X is 
1/2,0,0, and M is 1/3,1/3,0; I'm not sure for your lattice, but you can 
check online, like here: 

You can run matdyn as many times as you wish, it only takes a second.

Or you can even edit the force constant file and change the first line 
to specify ibrav 6 instead of 0 (and remove the 3 following lines which 
are the unit cell axes)

In any case, it will take less then 4 days and you will learn something 
in the process.


> Eleni
> Quoting Lorenzo Paulatto <paulatz at gmail.com>:
>> On 02/19/2018 03:14 PM, Saif Ullah wrote:
>>> Dear Eleni,
>>> Did you use ibrav=0? If so, then you need to use q_in_band_form=.false.
>>> q_in_cryst_coord=.true.
>> Neither of these two bits of advice is correct:
>> 1. q_in_band_form can be used with ibrav=0 as usual, and works just as
>> well as long as you specify the point coordinates
>> 2. there is no specific reason to use crystal coordinates with ibrav=0,
>> you can, as usual, but by no mean you "need to"
>> kind regards
>> --
>> Lorenzo Paulatto - Paris
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Lorenzo Paulatto - Paris

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