[Pw_forum] Gipaw - Magnetic susceptibility

[Ambrozio]

Thank you very much.

Alan.

2017-05-13 11:09 GMT-03:00 Davide Ceresoli <davide.ceresoli at cnr.it>:

> 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 Física
> > Mestre em Eng. de Materiais
> > Doutorando em Física - 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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-- 

Alan J. Romanel Ambrozio
Bacharel em Física
Mestre em Eng. de Materiais
Doutorando em Física - PPGFis
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