[DFTB-Plus-User] Setting non-periodic boundaries using a vacuum region

[Pasan Henadeera]

Dear developers and users,

I am new to the DFTB+ package, and am currently following through the
tutorials. While I was reading the Geometry section of the manual, I noted
that several boundary conditions are allowed within the gen format.
However, it is not clear to me on how the boundaries should be set for
either a nanowire or a nano-sheet. Please be kind enough to guide me on the
following scenarios.

1. For the case of a single nanowire, would the `H` boundary condition be
suitable? What is meant by helical cells?
2. If I have a 2D nanostructure, would it be advisable to apply the `S`
boundary condition while maintaining a vacuum in the non-periodic
direction? If so, how much of a vacuum should I consider?
3. Can the process in step 2 be used to model a 1D nanowire, with vacuums
in two directions? If so, would it be similar to the result obtained if the
`H` boundary is used (assuming that `H` is suitable to analyse a nanowire)?



Thank you
-- 
Best regards
Pasan Henadeera
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.zfn.uni-bremen.de/pipermail/dftb-plus-user/attachments/20220105/3149d11f/attachment.htm>