Geometry optimization issue

[Jahanzaib]

Dear Expert
I am facing alot of issues in geometry optimizations -  I just optimized FeSn cluster on my stanene ribbons - I have run my calculation on cluster - but it took more then 4 days still not optimized. I have attached graph so please guide me.
- I have attached the inputfile (output file is too big- not attached) of my system have following geometry optimization parameters   
    max_forces=0.1*eV/Ang,
    max_stress=0.2*GPa,
    max_step_length=0.005*Ang,
- In addition, I tried different 3 other options where I changed force, stress and step size
1) max_forces=0.01*eV/Ang, max_stress=0.02*GPa, max_step_length=0.2*Ang,
2) max_forces=0.01*eV/Ang, max_stress=0.02*GPa, max_step_length=0.0005*Ang,
3) max_forces=0.03*eV/Ang, max_stress=0.05*GPa, max_step_length=0.001*Ang,

Can you some one look into my file and guide me what I am doing wrong or why the geometry is not optimized?

Thank you

[AsifShah]

Hi,
Although I am not sure if this is the right way for magnetic materials but here is the following:
1. Try first optimizing using unpolarized spin GGA.PBE then use optimized geometry to optimize for spin polarized, SGGA.PBE.
2.  Increase your k points. (1x1x1 is very low)
3. Reduce damping_factor to 0.01 and increase max_steps=300
4. Keep max_step_length as default.

[Jahanzaib]

Thank you for your response.

My cell is very large in periodic direction having 165 atoms so I don't think I need large k points? I haven't adjust damping factor  - I will adjust them and let's c.
Do you think with very large unit cell, i need larger k points? In principle, if a unit cell is large, then fewer k points are enough.

Thank you

[AsifShah]

Hi
I would still recommend increase K points to at least to 3x3. Maybe it will help.