I am currently studying Siesta (specifically Transiesta) to investigate electronic transport in materials. However, I am confused about the assumptions and applicability of the NEGF method and this software.

Is it necessary for NEGF or Transiesta to assume ballistic transport of electrons? If so, how can I ensure this when building a model? A solid-state physics professor believes that "To use the non-equilibrium Green's function method, both conditions of ballistic transport and no reflection at the contacts must be satisfied" while I read in a doctoral dissertation that "Landauer's formula mainly focuses on ballistic transport, but NEGF has a wider range of applications." Can I assume that NEGF does not require the assumption of ballistic transport when solving the model, and that the assumption is only used when calculating the transmission coefficient and current using Landauer's formula?

Please correct me if I have any misconceptions, as I am not a student majoring in physics. Thank you.

  • $\begingroup$ +1 and welcome to our new community! We hope to see much more of you in the future, and thank you so much for contributing your question here! Your original post looked to me like it was two questions in one post, which we don't allow, so I've commented out what looked like a second question, and you're welcome to ask that one separately if you want! $\endgroup$ Apr 11, 2023 at 2:59
  • $\begingroup$ Thanks, I will create a new question. $\endgroup$
    – Ming
    Apr 11, 2023 at 3:04

1 Answer 1


Electron transport is a multi-faceted problem.

The most simple calculation is the ballistic approach where phase-coherence is assumed through the ballistic nature of the electrons.

When dealing with a higher level of accuracy one could look into inelastic transport which is due to electron-phonon interactions (electrons may scatter at phonons transferring momentum).

There may be other effects as well.


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