Table 1. Optimized Distances (d) between the O Atom of the Sulfonic Acid Group Protonated in the Initial Structures and Protons and the O Atom of the Closest Water Molecule in Hydrated Nafion and SPK Membrane Models (Å).

	d(−SO2O···H)		d(−SO2O···H···OH2)
λ	SPK	Nafion	SPK	Nafion
λ = 0	0.97 (0.97)	0.97
λ = 1	1.00 (1.00)	1.01	2.60 (2.59)	2.56
λ = 2	1.03 (1.04)	1.06	2.52 (2.49)	2.46
λ = 3	1.49 (1.53)	1.58	2.50 (2.52)	2.54
λ = 4	1.81 (1.81)	1.88	2.72 (2.71)	2.75