[Pw_forum] Pw_forum Digest, Vol 118, Issue 12

Sun May 14 20:23:43 CEST 2017

Dear Mohammadreza Hosseini,

   Please try to understand the concept of "back-folding" when using 
super-cells hen calculating band structures. There are programs to 
"unfold" the band structure, for example by Jonas Björk.

   And please do not reply directly to the Digest-messages; use an 
appropriate Subject and post only the relevant part of the Digest-message 
- or start a new thread, if there is nothing in the digested message that 
you refer to, like in your case. Thank you. :)

     Greetings from the aeroport of Lisbon,

        apsi

-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
   Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
     Ecole Normale Supérieure (ENS), Département de Chimie, Paris
     Mobile (F) : +33 789 37 24 25    (CH) : +41 79 71 90 935

On Sun, 14 May 2017, Mohammadreza Hosseini wrote:

> Dear All
>
> I am calculating the band structure of phagraphyne. First we computed for primitive unit cell and then for the 2X2 supercell. Although the bulk structure is same the band structure is different. What is the problem ?  Should parameters be optimized again for supercell?
>
> Mohammadreza Hosseini
> Tarbiat modares uiversity
> ________________________________________
> From: pw_forum-bounces at pwscf.org <pw_forum-bounces at pwscf.org> on behalf of pw_forum-request at pwscf.org <pw_forum-request at pwscf.org>
> Sent: Saturday, May 13, 2017 10:00 PM
> To: pw_forum at pwscf.org
> Subject: Pw_forum Digest, Vol 118, Issue 12
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> Today's Topics:
>
>   1. Re: how to determine the symmetry of a given phonon mode  in
>      quantum espresso (Lorenzo Paulatto)
>   2. Re: Gipaw - Magnetic susceptibility (Davide Ceresoli)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 13 May 2017 15:08:04 +0200
> From: Lorenzo Paulatto <lorenzo.paulatto at impmc.upmc.fr>
> Subject: Re: [Pw_forum] how to determine the symmetry of a given
>        phonon mode     in quantum espresso
> To: PWSCF Forum <pw_forum at pwscf.org>
> Message-ID: <1728518.gkaUiGcZ5e at paulaxps>
> Content-Type: text/plain; charset="iso-8859-1"
>
> On Friday, 12 May 2017 23:44:33 CEST Mihiri Hewa bosthanthirige wrote:
>> Hi,
>> I am graduate student at Clemson university, currently working with Quantum
>> Espresso. I would like to know how to determine the symmetry of a given
>> phonon mode in quantum espresso.
>
> Hello,
> it is printed in the output of phonon at the end of the calculation, i.e.:
> ...
>    End of self-consistent calculation
>
>
> --
> Dr. Lorenzo Paulatto
> IdR @ IMPMC -- CNRS & Universit? Paris 6
> +33 (0)1 44 275 084 / skype: paulatz
> http://www.impmc.upmc.fr/~paulatto/
> 23-24/4?16 Bo?te courrier 115,
> 4 place Jussieu 75252 Paris C?dex 05
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> ------------------------------
>
> Message: 2
> Date: Sat, 13 May 2017 16:09:02 +0200
> From: Davide Ceresoli <davide.ceresoli at cnr.it>
> Subject: Re: [Pw_forum] Gipaw - Magnetic susceptibility
> To: PWSCF Forum <pw_forum at pwscf.org>
> Message-ID: <6933968b-d5f1-fb6b-c518-e47ca4ce6da8 at cnr.it>
> Content-Type: text/plain; charset=windows-1252; format=flowed
>
> Dear Alan,
>     I think that there is no problem in doing a G=0 response
> with a shifted mesh. The response is at G=0, hence it couples
> wfcs at the same k. The susceptibility depends a lot on k-points
> sampling and if your system has a vanishing band gap, convergence
> can be a nightmare.
> By default the macroscopic shape is diagonal:
>   nmr_macroscopic_shape(:,:) = 0.d0
>   nmr_macroscopic_shape(1,1) = 2.d0 / 3.d0
>   nmr_macroscopic_shape(2,2) = 2.d0 / 3.d0
>   nmr_macroscopic_shape(3,3) = 2.d0 / 3.d0
> You can change the component (demagnetizing field) in the input file.
>
> Good luck for your calculations!
>
> Best,
>     Davide
>
>
>
> On 05/12/2017 07:47 PM, Ambrozio wrote:
>> Dear QE users and Developers,
>>
>> I'm working with NMR calculations in Gipaw. Recently I did some shielding
>> calculations and I have some questions regarding the magnetic susceptibility.
>> The article from developers Mauri et al (*PRL 77, 26, 1996*) explain that the
>> shielding of a bulk of a periodic system is also periodic (i.e. has the same
>> periodicity of *G*, the reciprocal lattice vectors), and it is proportional to
>> the magnetic susceptibility matrix. In the paper Mauri did a short discussion
>> about the macroscopic susceptibility, which is calculated at *G=0*. Follow my
>> questions:
>>
>> i) Assuming that the macroscopic susceptibility is calculating at gamma point
>> (*G=0*) and depends of the sample's shape, Does make sense to do a NMR
>> calculation with automatic kpoints (monkhorst pack grid)  that does not include
>> the gamma point? It is mandatory to including the gamma point when the shape
>> correction is .true.?
>>
>> ii) Does the susceptibility depends of the supercell size? I found very
>> different susceptibilities for the same material (AB graphite) changing the
>> supercell size.
>>
>> iii) Why the susceptibility  matrix is not diagonal when the shape correction is
>> .true.? Assuming the Mauri paper I think it doens't make sense. Help me to
>> understand...
>>
>>
>> I appreciate any help,
>>
>> Thanks in advance,
>>
>>
>> Alan.
>>
>>
>>
>> --
>>
>> Alan J. Romanel Ambrozio
>> Bacharel em F?sica
>> Mestre em Eng. de Materiais
>> Doutorando em F?sica - PPGFis
>>
>>
>>
>
> --
> +--------------------------------------------------------------+
>   Davide Ceresoli
>   CNR Institute of Molecular Science and Technology (CNR-ISTM)
>   c/o University of Milan, via Golgi 19, 20133 Milan, Italy
>   Email: davide.ceresoli at cnr.it
>   Phone: +39-02-50314276, +39-347-1001570 (mobile)
>   Skype: dceresoli
>   Website: http://sites.google.com/site/dceresoli/
> +--------------------------------------------------------------+
>
>
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> End of Pw_forum Digest, Vol 118, Issue 12
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