[BUG] Non-orthogonal cells do not evaluate correctly using the batch_eval() method

[Chronum94]

Non-orthogonal cells almost certainly have a bug in their force and energy evaluations.

In the figure below, I'm plotting E/atom as a function of a given generalized coordinate. The MACE-MP-0 large model (with L2 message passing) was used for the target data. Every energy curve except the one for the hex cell is in some reasonable degree of agreement.

[Tetracarbonylnickel]

After analysing your problem I could boil it down to the batch_eval() method of our calculator. If you loop over the atoms this schould not occur.

for atoms in atoms_list:
    atoms.calc = calc
    
 energies = [atoms.get_potential_energy() for atoms in atoms_list]

Does this occur in MD simulations with apax or are these trajectories that were labeled with the apax but generated with an other method?