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constraining magnetic field
Date: 2020/03/07 18:26
Name: Yun-Peng Wang   <yunpengwang@csu.edu.cn>

Dear OPENMX authors and users,
I am looking into the constrained noncollinear SOC feature. Since the direction and/or the magnitude of magnetic moments are constrained, there shall be a "constraining magnetic field" on each magnetic site. How can I find the "constraining" field from OPENMX calculations?

best wishes,
Yun-Peng Wang
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Re: constraining magnetic field ( No.1 )
Date: 2020/03/08 09:12
Name: T. Ozaki

Hi,

As for the constraint by the Zeeman term, one can easily find the local magnetic field.
On the other hand, as for the constraint scheme explained at
http://www.openmx-square.org/openmx_man3.9/node113.html

one can deduce "constraining magnetic field" from the constraint energy expression
shown at Eq. in the page 23 of
https://t-ozaki.issp.u-tokyo.ac.jp/ISS18/slides-1st/6-NCDFT-Ozaki.pdf

where Ni corresponds to Ns in Eq. 100 in the technical note:
http://www.openmx-square.org/tech_notes/tech2-1_0.pdf

Regards,

TO


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Re: constraining magnetic field ( No.2 )
Date: 2020/03/08 22:09
Name: Yun-Peng Wang  <yunpengwang@csu.edu.cn>

Dear Professor Ozaki,

Thanks for your quick response.
To make myself clear, I am interested in the constraining magnetic field after setting "scf.Constraint.NC.Spin On". The Equation in page 23 of the 6-NCDFT-Ozaki.pdf is what in my mind, from where the expression of constraining magnetic field is easy to deduce. I am only interested in the spin moment and the effective magnetic field on spin moments. I am not familiar with the OPENMX code structure, so I still need your help to point out where or which subroutine should I look into for finding the local magnetic field? I can try to find a simple way to print the local magnetic field, I believe the local field is already somewhere in the code, or it can be evaluated straightforwardly. I will feed back if I can figure it out.

Best wishes,
Yun-Peng Wang
メンテ
Re: constraining magnetic field ( No.3 )
Date: 2020/03/09 10:03
Name: T. Ozaki

Hi,

The relevant routine is make_NC_v_eff() in Occupation_Number_LDA_U.c.
The DFT+U methods, the constraint schemes, and the Zeeman terms all take the same form
for the effective Hamiltonian as described in Eq. 124 in
http://www.openmx-square.org/tech_notes/tech2-1_0.pdf

The v_effecitve are calculated in make_NC_v_eff().
The Zeeman term might be easy to understand for you. Once you make sure how it is implemented,
you may be able to understand how the v_effective for the constraint schemes are calculated in
the same routine.

Regards,

TO




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