Build silicene nanoribbons

[bfazi]

Hello every body

In ATK, how can we build a zig-zag and an armchair silicene nanoribbon?

[kstokbro]

Check the tutorial:
https://docs.quantumatk.com/tutorials/opening_a_band_gap/opening_a_band_gap.html

i.e. build bilayer graphene armchair or zig-zag,
 change C into Si,
relax

Edit: Updated link

[Tue Gunst]

Alternatively you can use the nanoribbon plugin tool:
Open the builder and ”add-> From Plugin->nanoribbon”.
Change the elements to Si instead of C.
Change the bond length to 2.2286 Å.
Choose the desired edge (zigzag or armchair) and width.
Click Build.

The most stable configuration of Silicene is not planar but is buckling – e.g. every other atoms is displaced in the out-of-plane direction.
For small ribbons you can impose the buckling by marking every other atom (All atoms of type A for instance) and use “Coordinate Tools-> Translate” to displace them 0.44 Å in the out-of-plane direction.
Alternatively you can click the rattle tool a few times and perform a relaxation as discussed in the tutorial on bulk silicene:
https://docs.quantumatk.com/tutorials/opening_a_band_gap/opening_a_band_gap.html

Edit: Updated link

[Anders Blom]

Try Cerda for Si and Muller or Hoffman for H.

[Mubashir hamid]

Although I tried Optimizing the geometry of the silicene nanoribbon by following the steps given in the tutorial, however, there was no buckling in the silicene nanoribbon. I built the silicene nanoribbon by using the plugin tool in the software and replaced the carbon atoms with Si atoms. I also chose the bond length of 2.286 for the nanoribbon. After that I clicked on the rattle tool a few times and sent the configuration for optimization. Still there is no buckling in the geometry.   

[Anders Blom]

Did you make sure to optimize with DFT? Forcefields might not get it right.

[Mubashir hamid]

Yes, I used DFT for optimization. Still there was no buckling. If you have made it already, can you please share the CIF of the nanoribbons of ZSiNR and ASiNR

[Anders Blom]

The procedure in the tutorial works perfectly well, I just tried it, it takes just a few minutes to set up and 1 minute to run on a laptop. It's a good exercise. But I didn't optimize the whole nanoribbon, just the 2-atom Silicene "crystal".  After you have that you can start building nanoribbons etc.

[Mubashir hamid]

Indeed the procedure works fine for building two atom silicene and germanene. However, it is the building of nanoribbons that gives problems. Could you please provide the detailed process of building nanoribbons from buckled (two atom) silicene/germanene.

[Anders Blom]

Same as making graphene ribbons really.

First, if needed, force the system into hexagonal using the Lattice Parameters tool (keeping the fractional coordinates fixed), since it might be slightly out of the hexagonal configuration after the geometry optimization.

Then create a supercell with A'=A+B and B'=B-A (see screenshot)

Now you have a rectangular building block that you can turn and repeat and terminate as you need for a ribbon.

[Mubashir hamid]

By following this procedure would the ribbon formed be zigzag or armchair

[Anders Blom]

Neither, it's still periodic in both directions in the plane. So it's not a nanoribbon, it's an infinite nanosheet still. The zigzag/armchair depends which direction you cut along, just like for graphene, as shown e.g. in https://www.eurekalert.org/multimedia/pub/79039.php

[Mubashir hamid]

would the same method work for building the nanoribbons of other buckled 2D materials like stanene, plumbene etc. as well

[Anders Blom]

For sure :-)

[Mubashir hamid]

Earlier you said, to get a nanoribbon out of a nanosheet I have to cut it into the particular direction. Do I need to perform a swap axes operation to get a zigzag/armchair oriented nanoribbon? If yes, please tell me which swap axes operations to perform for zigzag and armchair nanoribbons respectively.