[Wien] How to flip only one atom’s spin in ferromagnetic supercell ?

[Fecher, Gerhard]

Dear Min Lin,
to flip the spin of a particular atom 
first use 
==> 3.“label” an atom (put a 1 in the 3rd column next to the element name) to make this atom unique (needed eg. for core-holes)
(maybe you need to create first a P1 cell to have individual access to all atoms in the cell, but this you should already have from your supercell creation)
then use
==> instgen_lapw during initialisation to set the initial spin direction up or down (or edit case.inst)

sgroup will find the changed symmetry using the "numbererd" atoms 
this symmetry is independent on the spin s group just realizes that something at this atoms is different, 
the resulting symmetry may be different if you use spin-orbit interaction and do not change only up/down but also the spin direction.

Note: it is not necessary that the initial spin orientations (up/down) are kept during the scf cycle.

Ciao
Gerhard

DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
"I think the problem, to be quite honest with you,
is that you have never actually known what the question is."

====================================
Dr. Gerhard H. Fecher
Institut of Inorganic and Analytical Chemistry
Johannes Gutenberg - University
55099 Mainz
and
Max Planck Institute for Chemical Physics of Solids
01187 Dresden
________________________________________
Von: Wien [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von 林敏 [20520180155215 at stu.xmu.edu.cn]
Gesendet: Mittwoch, 18. September 2019 03:01
An: wien at zeus.theochem.tuwien.ac.at
Betreff: [Wien] How to flip only one atom’s spin in ferromagnetic supercell ?

Dear Wien experts,

For special reasons, I need flip only one atom’s spin in ferromagnetic supercell.

As we know, non-equivalent atoms will be reduced by “x symmetry” for supercell in init_lapw, and this reduction can be prevent by lowering the symmetry. There are four methods listed on User’s guide (10.4 Supercell calculations on TiC):

1.delete an atom (to simulate a vacancy)
2.replace an atom by another element (impurity)
3.“label” an atom (put a 1 in the 3rd column next to the element name) to make this atom unique (needed eg. for core-holes)
4. displace an atom (for phase transitions or phonons)

In my understanding, these all lower geometry symmetry. So, Lower the symmetry of electronic structure (flipping only one atoms’ spin) doesn’t work? Is there another method for prohibiting the reduction of number of non-equivalent atoms?

I really appreciate if any suggestions.

———————————————
Min Lin
2018 Ph. D student
Physical Chemistry
Chemistry Department Chemistry & College of Chemistry and Chemical Engineering
Xiamen University
China
e-mail: linmin at stu.xmu.edu.cn<mailto:linmin at stu.xmu.edu.cn>