[Pw_forum] sorting phonon bands based on symmetry/eigenvectors

[Derek Stewart]

Hi Miguel,

Thank you for your quick response and advice.  I agree that with the 
cheap cost of calculating phonon points once you have the IFC, a visual 
inspection of the plot is usually enough to order the phonon dispersion 
along a given symmetry line in the Brillouin Zone.

However, I would like to be able to sort the phonon frequencies for a 
large number of q-vectors in the Brillouin zone (not just restricted to 
a single symmetry line) and for this it would be very helpful if I can 
automate the process.

I know that for electronic bands, it is possible to determine the 
symmetry character of a given electronic band using sym_band.f90.  Would 
it be possible to use the same subroutines to determine the symmetry 
character of the phonon bands?  I could then sort based on this output.  
If anyone has some thoughts on this, I would be very interested.

Thanks,

Derek

################################
Derek Stewart, Ph. D.
Scientific Computation Associate
** New Webpage **
http://sites.google.com/site/dft4nano/
250 Duffield Hall
Cornell Nanoscale Facility (CNF)
Ithaca, NY 14853
stewart (at) cnf.cornell.edu
(607) 255-2856




Miguel Martínez wrote:
> Dear Derek,
>
> I recently discovered that plotband.x is also able to plot phonon bands
> as well as band structures. Just set all the references to 0. In any
> case, if you have the IFC you shouldn't have issues distinguishing
> crossing from anticrossing. Adding more points to the dispersion bands
> is almost free, after all. At least it is in the smallish systems I've
> done phonon calculations for.
>
> Regards,
>
> Miguel
>
> On Mon, 07 Dec 2009 13:42:50 -0500 Derek Stewart
> <stewart at cnf.cornell.edu> wrote:
>   
>> Hi everyone,
>>
>> I was wondering if anyone has written a script or program to sort the 
>> phonon frequencies based on their band index or branch.  This would
>> be very helpful for both plotting and post-analysis.  Currently when
>> you use matdyn for a given set of q-vectors, it prints out the phonon 
>> frequencies in order from lowest to highest.  However, this does not 
>> take into account the possibility of band crossings which can lead to 
>> changes in the order of the bands.  Matdyn also prints out the 
>> eigenvectors for the phonons so it should be possible to analyze this 
>> and then sort them.   If someone has already addressed this issue, I 
>> would be very interested in any tools that can handle this.
>>
>> Thanks,
>>
>> Derek
>>
>> ################################
>> Derek Stewart, Ph. D.
>> Senior Research Associate
>> ** New Webpage **
>> http://sites.google.com/site/dft4nano/
>> 250 Duffield Hall
>> Cornell Nanoscale Facility (CNF)
>> Ithaca, NY 14853
>> stewart (at) cnf.cornell.edu
>> (607) 255-2856
>>
>>
>>
>>
>>
>>