Commonly used tight-binding models

Describe the feature A suite of tight-binding models typically used for testing and general purpose, lets first compose a list of useful tight-binding models:

• graphene, possible arguments should be t=-2.7, bond=1.42, also 3rd nearest neighbours
• zgnr/agnr?
• slater-koster methods for easier manipulation, see #140, this should be a wrapper around that solution
• implement a generic category which incapsulates the neighbours and types to do post-processing based on this

My idea would be to place this in a sisl_toolbox since then it isn’t really part of the core sisl team. It would encourage a broader addition of testing models if so desired.

[zerothi]

For graphene this is now implemented, see sisl_toolbox.models.graphene.hamiltonian.ref["simple"] which is the basic TB model.

For now it is not as customizable, and I wish it had some other constructs as well. But I think this is ok to get in ASAP. 😃

[pfebrer]

Hi Nick, there’s not much I can add to the discussion because I have very little experience, sorry 😃

But I think it would be great that in general you could pass custom first, second, third…(as many as you want) neighbour hoppings.

Also maybe some BondCategory might help to define strange things such as edges in ribbons (in bonds where not all atoms are AtomNeighbours(3), use this special hopping). I would say that the best way would be to first categorize all atoms and then use this categorizations for each bond (instead of calculating the atom categories for each bond individually).