Christoph Ortner

And the analogue with a non-ASE calculator and ASEAtoms

I can donut later or Stela can make a PR?

Pull request

I need to look at minimise!. Let’s see

On Optimisation we have a lot of experience and can help if you are interested. But this would only make sense if we can commit to some strategy going forward...

`FixedCell` and `VariableCell` would either become `DofManagers` or alternatively `VariableCell` could be the default while `FixedCell` just becomes another constraint to add to the system.

interesting - how would one implement this?

Are these just linear constraints on the cell matrix?

force as well?

But we would allow this *only* for linear constraints. Even then I'm a bit nervous... One also needs to incorporate the constraint into the preconditioners...