QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: Jahanzaib on July 4, 2023, 02:47

Title: Optimization Issue
Post by: Jahanzaib on July 4, 2023, 02:47

Dear Experts
- 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 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=0.2*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

Title: Re: Optimization Issue
Post by: Jahanzaib on July 4, 2023, 11:31

any one guide me?
why with different Force, stress values etc - my geometry is not converging?

Thanks

Title: Re: Optimization Issue
Post by: Anders Blom on August 4, 2023, 19:51

Since it's a cluster, optimizing the stress is meaningless, and yes it will cause slow convergence for the forces because the algorithm is often trying to change the size of the simulation cell, causing all kinds of numerical issues as well. Just optimize the forces, keeping the "lattice" (simulation cell) fixed.