[Wien] Structure optimization

[Laurence Marks]

Inlined

_____
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Gyorgi
www.numis.northwestern.edu

On Sat, May 19, 2018, 4:28 AM pluto <pluto at physics.ucdavis.edu> wrote:

> Dear Prof. Blaha, dead All,
>
> Thank you for recent answers, they solved my issues.
>
> I have another issue on position relaxation. I looked at UG and at
> README_5_3 mixer document, but this didn't solve my issues.
> I am trying to relax a symmetric 7 monolayer slab (5 layers for MgO with
> single Fe atoms on both sides, 12 atoms total) using the MSR1a method. I
> try to run commands such as
> runsp -fc 0.5 -ec 0.0001 -cc 0.001
> I see atoms slightly moving in *.struct file and after some iterations I
> have info in the *.dayfile that MSR1a is changed to MRS in *.inm file
> and the cycle converges.
>
> Now, even with -fc 0.01 I cannot get things symmetric, for Fe-O distance
> I keep getting around 2.139 A and 2.148 on opposite sides of the slab
> (optimized bulk lattice parameter of MgO is used for in-plane slab
> size). Is that the accuracy limit for positions?
>

If you correctly setup a symmetric slab, Wien2k would have made the Fe on
both sides the same. If it did not, then you have made a mistake.

Another issue is that when I am running ferromagnetic+SOC calculation
> for such relaxed structure then forces (printed at the end of *.scf
> file) become large again. Is that OK? Should I try position optimization
> with SOC (should be negligible effect for Fe)?
>

Forces are not implemented with SOC (they are wrong).


> Other questions:
>
> - Is there a difference between *.inm and *.inM files for MSR1a position
> optimization?
>

Yes

- How can I lock some atoms in position during structure optimization?
>

Fixing atomic positions is normally bad science based upon
misunderstandings of optimisation.


> Best,
> Lukasz
>
> --
> Dr. Lukasz Plucinski
> Group Leader, FZJ PGI-6
> Phone: +49 2461 61 6684
>
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