Siesta

How to set the "electrode extension or screening region" of the scattering region in transiesta~?

Asked by Jianjun Mao

Dear Nick,

Recently, I just wonder how long is enogh for the scattering region. Scattering region include the the a scatter (molecule, defect, et.al) plus the electrode extension-screening region, how can we definite the scatter and the screening regions in the scat.fdf files.

In this article(https://arxiv.org/ftp/arxiv/papers/1406/1406.2670.pdf), do you think the lenghs of scattering regions along zigzag and armchair are enough or OK?

Does the way TranSIESTA handles the definition of the electrodes and scattering regions similar to ATK?

Thanks a lot.~

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Nick Papior
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Nick Papior (nickpapior) said : 		#1

1. It is up to you to determine the length of the electrode screening region. There is no unique answer. A metal requires relatively short lengths while semi-conductors are extremely difficult and requires very long electrode regions (I would NOT recommend doing any semi-conductor unless you really know what you are doing).

2. I don't have any specific comments since I don't know the paper and can't comment on it.

3. They are in many ways similar. ATK handles the electrostatics somewhat differently (better) from what I've gathered. But they share many similarities (as far as I know).

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Jianjun Mao (jjmao) said : 		#2

Dear Nick,

Thanks a lot~ For question 1, I mean--If we want to extend the length of screening region (electrode extension) in the scattering region. What should we do? Just extend the electrode proportion in the scattering region? Does these atoms in the electrode extension need to be constrained? How to definite these atoms in the scatXX.fdf? "TS. Atoms.Buffer" or ?

Many thanks~

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Nick Papior (nickpapior) said : 		#3

You attach more electrode layers. And yes, by all means, keep them constrained (as that would be most bulk-like). The extended electrode region has nothing to do with buffer atoms.

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Jianjun Mao (jjmao) said : 		#4

Dear Nick,

Thanks for your patience reply, for the electrode layers in the sattering region, how can I "constrain" them to distinguish them from the middle part?

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Best Nick Papior (nickpapior) said : 		#5

Like any other extended electrode layer. Please see the discussion in this article: https://www.sciencedirect.com/science/article/pii/S001046551630306X

I.e. you basically don't need to do anything.

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Jianjun Mao (jjmao) said : 		#6

Thanks Nick Papior, that solved my question.