QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: bera.1 on March 18, 2018, 11:04

Title: convergence problem in device with metallic gate and dielctric
Post by: bera.1 on March 18, 2018, 11:04

I am facing a problem in ATK when I am using a metallic gate and dielectric into a device with gold as right and left electrodes and MoS2 monolayer as a channel material. When I calculate zero bias transmission spectra and I-V characteristics of two terminal device that is without adding metallic gate and dielectric the calculation is converged and I get I_V curve. But when I add a metallic gate with gate voltage -1volt and dielctric of dielectric constant=4 then some points are not converging. And when I change the dielectric constant to a value of 9 and 25 then no points are converging and my calculation stops.
I have done same calculation with DTB molecules as a channel and also test for graphene with adding gate and dielectric then there is no problem in calculation and I have got I-V curve correctly.
So is there any problem with MoS2 in ATK?
Please help me in this issue.

Title: Re: convergence problem in device with metallic gate and dielctric
Post by: Ulrik G. Vej-Hansen on March 19, 2018, 10:15

Convergence is not always easy for more complicated devices, but we have just published this guide to help with that: https://docs.quantumwise.com/technicalnotes/negf_convergence_guide/negf_convergence_guide.html

I suggest you go through it and apply the suggestions which apply to your case. Have you converged the device with gate and dielectric at zero bias?

Title: Re: convergence problem in device with metallic gate and dielctric
Post by: bera.1 on March 19, 2018, 15:58

Thank you very much Ulrik G. Vej-Hansen for your valuable suggestion.
Yes the device is converged at zero bias with gate and dielectric but there is problem when i am changing dielectric constant to a higher value.

Title: Re: convergence problem in device with metallic gate and dielctric
Post by: Ulrik G. Vej-Hansen on March 19, 2018, 16:48

When you change the dielectric constant, you also change the system, so it is expected that the two situations can have different convergence behavior. I expect that the suggestions in the guide can help you solve the problem.