Figure 4.

Water exchange in the first hydration shell of Mg²⁺. (A) Kinetic rate coefficients k (eq S3) of microMg (blue) and nanoMg (green) of different water models (SPC/E,⁴⁶ TIP3P-fb,⁴⁷ TIP4P/2005,⁴⁸ TIP4P-Ew,⁴⁹ and TIP4P-D⁵⁰) and for TIP3P from the literature.²⁶ The gray vertical line indicates the experimental values^73,74 (Table 4). (B) One-dimensional free energy profiles as a function of the distance between Mg²⁺ and the leaving water molecule R_Mg–Ox for different force fields in combination with SPC/E water. (C) The snapshots show representative conformations in the two stable states: (i) Before exchange: Leaving water (shown in green) is part of the first and entering water (shown in blue) is part of the second hydration shell. (ii) After exchange: Leaving water is in the second hydration shell and the entering water molecule filled the void in the first hydration shell. The snapshots were taken using microMg(SPC/E).