[Pw_forum] Pw_forum Digest, Vol 118, Issue 12

Sun May 14 15:43:55 CEST 2017

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
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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)

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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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