[QE-users] Issue with highest frequency optical band phonons at gamma point in GaN

[Nicola Marzari]

Dear Bradly,

without seeing the image (wasn't there in the google folder) the obvious 
guess is that phonons in polar materials require a special treatment - 
maybe have a look at 
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.43.7231 or 
https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.73.515

A summary by Paolo Giannozzi on using PHonon is here:
http://www.fisica.uniud.it/~giannozz/QE-Tutorial/

			nicola



On 24/03/2020 23:27, Baer, Bradly wrote:
> Hello everyone,
> 
> I am attempting to generate the phonon dispersion plot for ZincBlende 
> GaN.  The highest frequency optical band of the dispersion is producing 
> the wrong result at the gamma point.  The rest of the dispersion looks 
> correct for the most part.  Below is a link to a google drive folder 
> with a copy of my current input and output files.  It also has an image 
> of the dispersion as plotted by plotbands.x.  I also tried the same 
> calculation in SiC and saw the same issue at the gamma point (both are 
> FCC).  Am I doing something incorrectly that would cause an issue at the 
> gamma point only?  I appreciate any advice on the matter.
> 
> https://drive.google.com/open?id=13WDzUBL3DNwasxsDR1gz47MIDh8LtMLZ
> 
> Thanks,
> Brad
> 
> --------------------------------------------------------
> Bradly Baer
> Graduate Research Assistant, Walker Lab
> Interdisciplinary Materials Science
> Vanderbilt University
> 
> 
> 
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-- 
----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, EPFL
http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project