[CP2K-user] [CP2K:21963] Re: Reproducing NEGF results

[Dmitry Ryndyk]

Dear Michael, 

to see the same result, as in the report, you should take zero voltage and 
other energy limits:

&PRINT
     &DOS
       FILENAME device
       FROM_ENERGY 0.272240982
       N_GRIDPOINTS 401
       TILL_ENERGY 0.492829218
     &END DOS
     &TRANSMISSION
       FILENAME transm
       FROM_ENERGY 0.272240982
       N_GRIDPOINTS 401
       TILL_ENERGY 0.492829218
     &END TRANSMISSION
   &END PRINT

The Fermi level is 0.38253510. The result is in attachment. It is not 
exactly the same, but it can be for many reasons.  

I am currently revising the NEGF code, and may change the energy levels to 
be around the Fermi level. If you want to use NEGF, I recommend the latest 
development version of CP2K. And I will try to answer further questions.  

Concerning your second question. It is the advantage of the NEGF approach 
that T(E) is changed with bias voltage. But as a simplest way to get I(V), 
the zero-voltage transmission can sometimes be used. Very carefully to make 
sense. It depends on the problem, of course. If the energy levels of the 
central system are not changed at finite voltage, one can omit 
self-consistency at finite voltage and use T_0(E).

Best wishes,
Dmitry Ryndyk

Michael LaCount schrieb am Donnerstag, 10. April 2025 um 05:20:41 UTC+2:

> I am trying to reproduce the transmission coefficient plot found in Figure 
> 4 of the CP2K Electron Transport based on Non-Equilibrium-Greens-Functions 
> Method: eCSE 08-09 Technical Report (see attached). From what I can tell 
> the system is the same as the one found 
> in 'QS/regtest-negf-fft/au111_c6h4s2_gamma_0.50V.inp'. However when I run 
> that job unmodified except to add print commands in the NEGF section (see 
> below) I don't get anything close to what was found in the Technical 
> Report. The job input and output files are attached.
>
> I also have a further question regarding this test. I want to create I-V 
> curves, from what I understand I should therefore use the zero bias 
> transmission coefficients, and set NEGF/CONTACT/ELECTRIC_POTENTIAL to 0 
> correct?
>
> Any clarity on where I am going wrong would be appreciated. 
>
>    &PRINT
>      &DOS
>        FILENAME device
>        FROM_ENERGY -0.2
>        N_GRIDPOINTS 401
>        TILL_ENERGY 0.2
>      &END DOS
>      &TRANSMISSION
>        FILENAME transm
>        FROM_ENERGY -0.2
>        N_GRIDPOINTS 401
>        TILL_ENERGY 0.2
>      &END TRANSMISSION
>    &END PRINT
>

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