QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: ramkrishna on February 26, 2014, 00:24

Title: Boundary conditions of FFT2D Poisson solver
Post by: ramkrishna on February 26, 2014, 00:24

Dear Sir,
      In case of 2 probe device system, the default Poisson solver is FFT2D in 13.8.0. Now,  it is showing Dirichlet boundary condition in the left and right C directions in the script generator window however if we export the script in the editor, then it gives periodic boundary conditions in all A, B, C directions. In case of 2 probe system it should be Dirichlet boundary condition in the transport direction, no? So, I am really confused, whether it is taking the Dirichlet condition or periodic condition in the calculations. Can you please clarify this?

Thanks
Ramkrishna

Title: Re: Boundary conditions of FFT2D Poisson solver
Post by: Umberto Martinez on February 26, 2014, 09:38

You are right,  in a device configuration the Dirichlet boundary conditions are set for the C direction.
The boundary conditions that are printed in the script are the ones for the left and right electrodes and are set to periodic in all three directions.

Select "show default" in the Script detail window when you save the script and all the parameters, including the default ones, will be printed in the script.
including the Poisson solver for the device:

Code

device_poisson_solver = FastFourier2DSolver(
    boundary_conditions=[[PeriodicBoundaryCondition,PeriodicBoundaryCondition],
                         [PeriodicBoundaryCondition,PeriodicBoundaryCondition],
                         [DirichletBoundaryCondition,DirichletBoundaryCondition]],
    order=2
    )

Title: Re: Boundary conditions of FFT2D Poisson solver
Post by: ramkrishna on February 26, 2014, 17:21

Dear Sir,
     Thank you for your reply.

So, is it taking the device Poisson solver inherently when I am running a job after saving a script by considering "minimal"? or should I have to include the device Poisson solver along with the electrodes within the code before submitting a job?

Thanks
Ramkrishna

Title: Re: Boundary conditions of FFT2D Poisson solver
Post by: Anders Blom on February 27, 2014, 00:08

The script you see with "show defaults" is what is actually used, even if you run the script made with "minimal". It's just that the "minimal" version is shorter and easier to see what is changed compared to defaults.

Title: Re: Boundary conditions of FFT2D Poisson solver
Post by: ramkrishna on February 27, 2014, 00:39

Dear Sir,
        Thanks a lot for the clarification.

Regards
Ramkrishna