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

[Nicola Marzari]

On 24/03/2020 23:54, Baer, Bradly wrote:
> Nicola,
> 
> The image is in the outputs folder as "gan.phonons.bands.ps" That is the 
> native output from the plotbands.x code as far as I know.  It is 
> possible that it has been slow to finish uploading from my computer to 
> the google drive though.

Thanks - it's there now, but it wasn't before - there were much fewer 
files. Anyhow, the LO-TO splitting is exactly the issue. Plenty of 
literature, but start from that listed.

			nicola



> 
> I will take a look at the links you provided and I appreciate you taking 
> the time to write your reply.
> 
> Thanks,
> Brad
> 
> --------------------------------------------------------
> Bradly Baer
> Graduate Research Assistant, Walker Lab
> Interdisciplinary Materials Science
> Vanderbilt University
> 
> 
> ------------------------------------------------------------------------
> *From:* Nicola Marzari <nicola.marzari at epfl.ch>
> *Sent:* Tuesday, March 24, 2020 5:36 PM
> *To:* Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>; 
> Baer, Bradly <bradly.b.baer at Vanderbilt.Edu>
> *Subject:* Re: [QE-users] Issue with highest frequency optical band 
> phonons at gamma point in GaN
> 
> 
> 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://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fjournals.aps.org%2Fprb%2Fabstract%2F10.1103%2FPhysRevB.43.7231&data=02%7C01%7Cbradly.b.baer%40vanderbilt.edu%7Cf6d82383087c4065e82a08d7d043c71f%7Cba5a7f39e3be4ab3b45067fa80faecad%7C0%7C0%7C637206861856438833&sdata=Gj4zzJGY%2F4QRFV6oBN83EmExNE%2F4LNuH3O7RgByRyFA%3D&reserved=0 
> or
> https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fjournals.aps.org%2Frmp%2Fabstract%2F10.1103%2FRevModPhys.73.515&data=02%7C01%7Cbradly.b.baer%40vanderbilt.edu%7Cf6d82383087c4065e82a08d7d043c71f%7Cba5a7f39e3be4ab3b45067fa80faecad%7C0%7C0%7C637206861856438833&sdata=neMQPei1nhq7HnGSESWkLMzfvGC6bJ2XZP3l3U9Qtig%3D&reserved=0
> 
> A summary by Paolo Giannozzi on using PHonon is here:
> https://nam04.safelinks.protection.outlook.com/?url=http:%2F%2Fwww.fisica.uniud.it%2F~giannozz%2FQE-Tutorial%2F&data=02%7C01%7Cbradly.b.baer%40vanderbilt.edu%7Cf6d82383087c4065e82a08d7d043c71f%7Cba5a7f39e3be4ab3b45067fa80faecad%7C0%7C0%7C637206861856448828&sdata=BMa2Mv%2Fr2wT9iCutYqRRcMugfMEBkvJTUAj9LKjXOxw%3D&reserved=0
> 
>                          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://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdrive.google.com%2Fopen%3Fid%3D13WDzUBL3DNwasxsDR1gz47MIDh8LtMLZ&data=02%7C01%7Cbradly.b.baer%40vanderbilt.edu%7Cf6d82383087c4065e82a08d7d043c71f%7Cba5a7f39e3be4ab3b45067fa80faecad%7C0%7C0%7C637206861856448828&sdata=%2BhHaIluljELkLOzsNDmP%2F2YfhboZrcCUGdBv7XhrCPc%3D&reserved=0
>> 
>> 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
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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