FIG. 3.

(a) Chemical structure and (b) crystal structure of naproxen H₂O·Mg²⁺. (c) Solvent density contours for oxygen from water [red, $g_{\text{O}}\left(r\right)=30.0$] and Mg²⁺ [green, $g_{{\text{Mg}}^{2+}}\left(r\right)=4000.0$], with colored spheres showing the locations of localized water molecules and ions as assigned in the refinement process. The large values of the pair distribution function at the contour surface indicate that the water oxygen atoms and magnesium ions are highly localized. In the case of magnesium, the value is particularly large due to its low concentration in the bulk liquid (Table I).