[Pw_forum] How to constrain the magnetization along z-axis

[Jeffrey Mullen]

Hello Jinsen,

I am working on this problem (in a different system) and, while I have not
been successful getting these to converge yet, I think that you need to
modify your system in the following way:

- remove the angle2(2) constraint
- change the constrained_magnetization to ''atomic direction"

It is my understanding that this will give your system a
starting_magnetization (in your case, -1.0) but will only constrain the mag
to a spin direction, not magnitude. In short, I think your file is
over-constraining the system and nothing is relaxing.

Please let me know if this helps, or if I am in error, as I am trying to
get some problems resolved myself and cannot seem to get passed them.

Cheers


Jeff Mullen, PhD
North Carolina State University

On Tue, Nov 21, 2017 at 2:09 AM, Jinsen Han <hanjinsen12 at nudt.edu.cn> wrote:

> Dear All,
>
>
>
> I want to calculate the magnetization along z-axis in a Chromium droped
> graphene system. There are two elements in the system: Cr and C. Here
> attatched the spin related part of input file:
>
> =================================
>
>   &system
>
>      ibrav=12,
>
>      celldm(1)=27.886706758, celldm(2)=1.0,  celldm(3)=1.5
>
>      celldm(4)=0.5,
>
>      nat=156,
>
>      nbnd=800,
>
>      ntyp=2,
>
>      ecutwfc=50.0, ecutrho=450.0
>
>      occupations='smearing', smearing='methfessel-paxton', degauss=0.01
>
>      noncolin = .true.
>
>      angle1(2)= 0,
>
>      angle2(2)= 0,
>
>      starting_magnetization(2)=-1.0,
>
>      constrained_magnetization='atomic'
>
>      nosym= .true.
>
>      london=.true.
>
>   /
>
>   &electrons
>
>     conv_thr =  1.0d-6
>
>      mixing_beta = 0.1
>
>   /
>
> ATOMIC_SPECIES
>
>   C  12.0     C.pbe-van_bm.UPF
>
>   Cr 52.0     Cr.pbe-sp-van.UPF
>
> =================================
>
> However, the output file (attached blow) shows that not only the magnetic
> moment of Chromium was constrained, but that of Carbon was also
> constrained. And the magnetization of Chromium has the x-y component
> besides z component.
>
> Which parameter shoud I change or add in the input file? Would you please
> give me any suggestion?
>
> =============================================
>
>      atom number    2 relative position :    0.0838   0.0483   0.0043
>
>      charge :     1.700856
>
>      magnetization :         -0.000007   -0.000000   -0.074105
>
>      magnetization/charge:   -0.000004   -0.000000   -0.043569
>
>      polar coord.: r, theta, phi [deg] :     0.074105  179.994790
> -178.968975
>
>      constrained moment :     0.000000    0.000000  -20.000000
>
> =============================================
>
>      atom number   38 relative position :    0.4168   0.2406   0.1135
>
>      charge :    11.552952
>
>      magnetization :         -0.000634    0.000521   -0.077706
>
>      magnetization/charge:   -0.000055    0.000045   -0.006726
>
>      polar coord.: r, theta, phi [deg] :     0.077710  179.394945
> 140.568470
>
>      constrained moment :     0.000000    0.000000   -1.000000
>
> =============================================
>
>
>
> Thank you!
>
>
>
> Best regards,
>
> Jinsen Han
>
>
> --
> Jinsen Han
>
> Department of Physics, 4-409
> College of Science
> National University of Defense Technology
> Changsha, 410073
> P.R. China
>
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