PBC with multiple molecules

[chuhong-wang]

Hi! Thanks for the open-source code and models, as well as the Numba version.

I have a question regarding the current support for PBC in simulation boxes containing multiple molecules. In the calculator.py file, there is a NotImplementedError with the message 'PBC with multiple molecules is not implemented yet.', which suggests that this feature may not be supported at the moment. I also noticed this issue from last year, which seems to indicate that development on this feature was underway.

Could you maybe provide clarification on whether support for multiple molecules with PBC is available or planned for future updates?

Thanks!!