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QuantumATK => General Questions and Answers => Topic started by: chitrapandy on January 6, 2020, 05:11

Title: OptimizationDevice Geometry
Post by: chitrapandy on January 6, 2020, 05:11

Hi,

I have created SiNWFET device geometry which is doped with single Phosphorus , Single Boron atom  in its central region and I try to optimize this using optimizeDeviceGeometry study object.
 Following error occurred during the optimization. Please help to rectify this error.
I have attached the device geometry python script and log file.

Title: Re: OptimizationDevice Geometry
Post by: hsuya on January 6, 2020, 07:57

I think you used extended huckel method for optimizing the geometry however it cannot be used to perform geometry optimization. Try using Slater Koster or other DFT methods.

Title: Re: OptimizationDevice Geometry
Post by: chitrapandy on January 7, 2020, 08:17

ok. I will try other calculators.
Thank you for your suggestion.

Title: Re: OptimizationDevice Geometry
Post by: chitrapandy on January 9, 2020, 05:31

when I run using the LCAO calculator for optimization i am getting the below warning

WARNING                                                                     
                                                                       
# The computed multigrid residual is greater than the required accuracy. #
                                                                           
# Computed residual :   4.44756e-10   #
# Required accuracy :   1.00000e-12   #


I don't understand what is the significance  can anyone pls tell about this warning?

Thank you

Title: Re: OptimizationDevice Geometry
Post by: Ulrik G. Vej-Hansen on January 10, 2020, 08:49

This means that the Poisson solver did not converge. You could try changing it, f.ex. to the Parallel Conjugate Gradient solver or increasing the mesh cutoff. You should also check that your gate and dielectric setup (if present) is reasonable.