vacuum level

[tara95]

hi
in a paper says :  A vacuum thickness of 12 Å in the x-direction and
a vacuum thickness of 15 Å in the y-direction are used to
decouple the periodic images .
How do I do this?

[Petr Khomyakov]

You can increase the lattice parameters in the corresponding directions to increase the vacuum  thickness. This can done using the Bulk Tools -> Lattice Parameters in the Builder.

[tara95]

That is, if I considered a ribbon, its distance from the next ribbon in the same direction is 15 or 12 angstroms?
So if I want to design a device that uses a dielectric for those 15 angstroms and a gate thickness of 5 angstroms, how can it be done with the 12-angstrom expressed? Are these two related?

[Petr Khomyakov]

No, they are not related, i.e., you can set the vacuum thickness in the two directions as you want.

[tara95]

So to adjust the vacuum level, I need to change the lattice parameters to make the ribbon spacing equal to 15 Angstroms.
What should I do now to simulate the same material as the vacuum is 15 Angstroms and the dielectric thickness is 20 Angstroms? Should I change the lattice parameter again to create a 20-angstrom space? I'm really confused. Please help me

[Petr Khomyakov]

Please take a look at the following tutorials on how to build nanoribbon devices:
https://docs.quantumwise.com/tutorials/vnl_graphene_transistor/vnl_graphene_transistor.html
https://docs.quantumwise.com/tutorials/graphene_nanoribbon_device/graphene_nanoribbon_device.html