QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: pervanem on June 13, 2021, 13:54

Title: the calculation did not converge to the requested tolerance (NEGF study)
Post by: pervanem on June 13, 2021, 13:54

I perform NEGF calculation for substituted (-CH3) graphene nanoribbon.
But I get converge issue?
I made maximum step=1000. I also get "the calculation di not converge to the requested tolerance" warning.
I think, this should be the last solution.  it has not been solved, yet.
 then,
https://docs.quantumatk.com/technicalnotes/negf_convergence_guide/negf_convergence_guide.html
I read above linked page.

K points= 1x1x150
mesh cut-off=150
is there an easy solution?

can you help me?

Title: Re: the calculation did not converge to the requested tolerance (NEGF study)
Post by: Anders Blom on June 16, 2021, 22:54

When you see very large charge transfer from one atom like Carbon number 235 (it has gained 12 electrons!) you can tell something is not physical in the simulation. it's not  a numerical issue, or convergence problem, but rather there is something strange with all those H atoms...  Since graphene is sp2, I am not sure you can just add CH3 (sp3) like that. And even if you can, the H atoms are too close to each other.

Title: Re: the calculation did not converge to the requested tolerance (NEGF study)
Post by: pervanem on June 17, 2021, 02:00

Thanks you for reply... :)