Our results indicate that electrostatic embedding in which the MM waters are described 13 by point charges is not sufficient for describing core-level IEs and that the IEs of the water molecules on the boundary are not accurate. Therefore, we used the following multi-layer scheme for the calculation of the spectra. We first computed all core IEs in the QM part-for example, for a calculation with 5 waters in the QM part, we computed 5 IEs.