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Representative geometries for configurations taken from the local minima of the free energy curves of Figure 1 for the contact ion pair state of (a) [CaHPO4]0; (b) [Ca(HPO4)2]2–; and (c) [Ca(HPO4)3]4–. Ca is cyan, P is tan, O is red, and H is white. Only those water molecules coordinated to calcium are shown for clarity.
