Christoph Ortner

The way I did it in JuLIP was to have a conversion interface e.g. ```julia _convert_positions(X::Vector) = X _convert_positions(X::AbstractVector) = collect(X) _convert_positions(X::AbstractMatrix) = # convert into vector of SVectors _convert_bc(bc::NTuple{3,...

If I have a unit cell as here ``` julia> AtomsBase.FlexibleSystem( bulk(:Si, pbc=true) ) FlexibleSystem(Si₂, periodic = TTT): bounding_box : [ 0 2.715 2.715; 2.715 0 2.715; 2.715 2.715 0]u"Å"...

Just add the rich display into the docs: ``` help?> AtomsBase.AbstractSystem AbstractSystem{D} A D-dimensional system. Use `rich_display(system)` for a plain-text visualisation. Suitable for small structures such as unitcells. ────────────────────────────────────────────────────────────────────────────────────── AbstractSystem(system::AbstractSystem;...

an alternative option could be to have the rich display as default but add a global variable in AtomsBase that I can change to make it slim.

And btw, I can't use semi-colons, because I do want a little bit of visual feedback.

@jameskermode maybe we can play with a `FlexAtom` struct building on the `ACE.State` implementation. This would allow for fully flexible fields, we could even distinguish static and dynamic fields, but...

@jameskermode - do you mean you want to just try locally whether my approach is sufficiently flexible for XYZ? Otherwise we could collaborate on a separate package that implements the...

James - why not publish this as a separate package independent of XYZ? We could start making ACE compatible with that, and then try it out with Molly etc? If...

Can this be closed?

My suggestion is ``` potential_energy(atoms, calc)::Number forces(atoms, calc)::AbstractVector{