Here, we assume that each ML atom functions as an independent isotropic polarizable center, with its associated induced dipoles being proportional to the electric field evaluated on its coordinates, E MM , which is generated exclusively by the MM point charges. The distortion energy, E D ML , is then calculated as half the negative value of the polarization energy. The only parameters that need to be assigned beforehand to the ML atoms are the atomic polarizabilities (and Lennard-Jones ones, but this is a common practice in QM/MM simulations, and are usually taken from MM force fields). Based on a previous study, the in vacuo atomic charges for the ML region are MBIS charges, the atomic polarizabilities are taken from the recommended values of static scalar dipole polarizabilities for neutral atoms and ε is set to 2.