Table 4. Comparison of Calculated and Observed Solvation Free Energies (ΔG_hyd, kcal/mol), and Ion–Water Oxygen Distances (M²⁺–O, Å) Using Our Parameter Set from Table 1 for Different Metals^a,b.

	TIP3P		SPC		experimental
	ΔGhyd	M2+–O	ΔGhyd	M2+–O	ΔGhyd54	M2+–O52
Fe	–451.9 ± 0.2	2.13 ± 0.04	–450.0 ± 0.1	2.14 ± 0.04	–451.8	2.12
Ni	–492.7 ± 0.1	2.06 ± 0.03	–490.8 ± 0.2	2.07 ± 0.03	–492.8	2.06
Co	–480.5 ± 0.1	2.08 ± 0.03	–478.7 ± 0.2	2.09 ± 0.03	–481.0	2.08
Zn	–483.4 ± 0.1	2.08 ± 0.03	–481.4 ± 0.2	2.09 ± 0.03	–483.3	2.08
Mn	–436.9 ± 0.2	2.19 ± 0.03	–433.1 ± 0.1	2.20 ± 0.04	–436.4	2.20
Mg	–454.4 ± 0.1	2.12 ± 0.04	–452.3 ± 0.1	2.13 ± 0.04	–454.2	2.10
Ca	–379.9 ± 0.2	2.38 ± 0.02	–377.9 ± 0.2	2.39 ± 0.01	–379.5	2.39–2.4676,77

^aCalculations were performed using both SPC⁴⁰ and TIP3P⁴¹ water models.

^bAll values are averages and standard deviations over five trajectories, as outlined in the main text. M–O distances for all of the water molecules bound to the metal were monitored along the simulation. Only for calcium, which shows a rapid water exchange, the M–O distance was directly taken from the peak of the RDF (see Supporting Information Figure S1).