def rescale_periodic_system(atoms1, atoms2):
    """
    Scales two periodic systems to the same size.
    Not the most efficient implementation yet.

    For a first implementation, I assume that the number
    of atoms in both cells is the same. Later, I will
    create supercells to fix this.


    Parameters
    ----------
        atoms1: ASE atoms object
        atoms2: ASE atoms object

    Returns
    --------
        atoms1_copy: ASE atoms object
        atoms2: ASE atoms object
    """
    atoms1_copy = atoms1.copy()
    atoms1_copy.set_cell(atoms2.get_cell(), scale_atoms=True)

    return atoms1_copy, atoms2