Using the Zn 2+ -F -distance as collective variable, we calculated the energy profile going from Zn 2+ -F -CIPs to free Zn 2+ and F -at three different temperatures by ab initio molecular dynamics, as shown in Fig. . It could be seen that Zn 2+ -F -CIPs is more stable than the outer-sphere complexes at all three temperatures, suggesting that the formation of CIPs is favorable in the aqueous ZnF2 solution in thermodynamics.