Thoughts before sprint

[ndaelman-hu]

These are just a bunch of notes from during the DPG 2024, to be applied during the sprint.

[ndaelman-hu]

Dimensionality vs periodicity

There are 3 ways to regulate dimensionality, depending on the restrictions of the code.

1. directly, i.e. dimensionality.
2. via periodic boundary conditions (PBC)
3. adding a vacuum along the axis to be excluded.

Currently, option 2 is broken (see below) and there's no option 3.
Lastly, we need an "interpreted / effective dimensionality" that encompasses all 3 options together, making them interoperable (maybe type?)

For option 2, we currently have

    periodic_boundary_conditions = Quantity(
        type=bool,
        shape=[3],
        description="""
        If periodic boundary conditions are applied to each direction of the crystal axes.
        """,
    )

My recommendations:

• Abbreviate the name. I think pbc is well-known enough.
• The shape should not be a constant. Else, we would end up in scenarios where we have 3 PBC axes for true 2D systems... They wouldn't be interpretable anymore.

[JosePizarro3]

Ok, feel free to change the naming. About the shape, I am not sure if I understand. For 2D system, pbc = [True, True, False] anyways. Or am I understanding that the shape should be set by dimensionality itself? In that case, they would end up being equivalent quantities.