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. Author manuscript; available in PMC: 2014 Oct 24.
Published in final edited form as: J Phys Chem B. 2013 May 30;117(42):10.1021/jp4020146. doi: 10.1021/jp4020146

Figure 10.

Figure 10

(A) The B3LYP//6-31G*/MM free energy surfaces calculated for the 1W and 2W proton transfer mechanisms for the (PO3− + H2O (or 2H2O)) system. (A) The 2D free energy surface in the ζ, R2 space, where ζ is the 1W PT coordinate defined as the difference between the proton-donor and proton-acceptor distances. (B) A comparison of the 1D free energy surfaces obtained along the ζ RC for the 1W PT path, obtained by WHAM (blue dots) and for the 2W PT path, obtained by WHAM (green dots) and using FEP/US (black dots). Note that here the proton acceptor is the second water for 2W PT and the oxygen of metaphosphate for 1W PT.