[Wien] Structure optimization

[pluto]

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?
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)?

Other questions:

- Is there a difference between *.inm and *.inM files for MSR1a position 
optimization?
- How can I lock some atoms in position during structure optimization?

Best,
Lukasz

-- 
Dr. Lukasz Plucinski
Group Leader, FZJ PGI-6
Phone: +49 2461 61 6684
https://electronic-structure.fz-juelich.de/