Since the LS to HS Fe-N elongation drive an overall small increase in the size of the complex, the geometry of the first solvation shell will find a new minimum. Figure The new nuclear arrangements and electronic density of the complex also affect distances between the water molecules themselves. On average, the O-O distance decreases by 0.051 Å from the LS to the HS state, for the 17-shell. Calculating the RMSD between the relaxed geometries of the water molecules in the two states, the 17-shell value of 0.320 Å is reduced to 0.200 Å for the 20-shell. Since the 17-shell contains the least amount of water molecules that still maintain the full hydrogen bond network around the complex, it makes sense that the individual waters need to rearrange themselves more to accommodate the changes in the solute structure, compared to shells with more water molecules. This tighter, slightly closer network of water molecules around the excited complex is consistent with the changes in the first peak of the OPLS/TIP4PEW RDFs shown in figure .