[Pw_forum] sorting phonon bands based on symmetry/eigenvectors

[Stefano Baroni]

Derek: I do not think/know that/if anything is implemented already, but you problem was elegantly addressed some time ago by Karin Rabe who introduced the concept of "vibrational Wannier function" (or something like that). You may want to browse the literature and report to us if you find anything meaningful/interesting. I maintain, though, that the process you want to automate can be automated using IFC as well. Cheers - Stefano

On Dec 8, 2009, at 4:07 PM, Derek Stewart wrote:

> 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
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
> 
> 
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---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center - Trieste
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