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Include spin orbit coupling but turn off magnetism
Date: 2016/04/23 13:08
Name: Hung-Yu Yang   <yanghw@bc.edu>

Dear developers,

Since I want to compare the non-magnetic and magnetic calculation, I am wondering is it possible to include spin orbit coupling in the calculation but turn off magnetism at the same time using openmx? In other software such as quantum espresso, I can achieve this by not setting initial spin occupations, but this way doesn't seem to work in openmx. Did I miss some keyword or this kind of calculation is not allowed in openmx? Any reply will be very helpful and well appreciated.

Yours sincerely,

Hung-Yu
メンテ
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Re: Include spin orbit coupling but turn off magnetism ( No.1 )
Date: 2016/04/24 09:39
Name: T. Ozaki

Hi,

An easy way for that purpose is to perform a non-spin polarized calculation within the colliear
DFT, and perform one shot diagonalization including SO coupling with the charge density obtained
by the first SCF calculation. Though this is known to be a second variational scheme, OpenMX
does NOT support the scheme. Instead of the scheme, in OpenMX one can control the direction and
magnitude of spin moment using the constraint scheme 'on2' explained at
http://www.openmx-square.org/openmx_man3.8/node106.html
This is a more general scheme which allows us to include SO coupling in a self-consistent manner
while controlling the spin polarization within the non-colliear DFT. With 'on2', if you start the
calculation with a non-spin polarized charge density, the electronic structure will be constrained
so that the non-spin polarized state can be kept as much as possible depending on the magnitude
of 'scf.Constraint.NC.Spin.v'.

Regards,

TO
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Re: Include spin orbit coupling but turn off magnetism ( No.2 )
Date: 2016/04/25 02:41
Name: Hung-Yu Yang  <yanghw@bc.edu>

Dear Prof. Ozaki,

Thank you for pointing out this direction; actually I thought about using constraint to achieve this, while when I checked the manual of 3.7 version, only the constraint on the spin direction was allowed and I didn't check the newest 3.8 version. Thank you again for the helpful information.

Yours sincerely,

Hung-Yu
メンテ
Re: Include spin orbit coupling but turn off magnetism ( No.3 )
Date: 2016/04/25 08:52
Name: T. Ozaki

Hi,

One more tips:
In OpenMX Ver. 3.8, the 'RMM-DIISH' has been newly released as explained in
http://www.openmx-square.org/openmx_man3.8/node42.html
The scheme applies RMM-DIIS for the KS Hamiltonian matrix, and thereby may be suitable for
the plus U method and the constraint schemes. In several cases, we found that RMM-DIISH
outperforms RMM-DIISK. I wonder that the scheme can be an option for your case.


Regards,

TO
メンテ
Re: Include spin orbit coupling but turn off magnetism ( No.4 )
Date: 2016/04/27 21:51
Name: Hung-Yu Yang  <yanghw@bc.edu>

Dear Prof. Ozaki,

What I am doing really involves both plus U and constraint (iridates), and this can possibly make a difference. Thank you very much for the update.

Yours sincerely,

Hung-Yu
メンテ

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