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. Author manuscript; available in PMC: 2014 Jan 8.
Published in final edited form as: J Chem Theory Comput. 2012 Dec 12;9(1):153–164. doi: 10.1021/ct300703z

Figure 3.

Figure 3

The free energy profiles calculated with different methods for the Na+:Cl− pair from a 21-window umbrella sampling simulation with a strong biasing potential of 100 kcal/mol-Å2. The upper left panel shows the results from all methods with 21 windows. Other panels show the results from individual methods with different numbers of windows: 6 (red), 11 (blue), and 21 (black) windows. All methods, including UI, converge with 21 windows and give similar results. With 11 windows, however, MBAR fails to produce correct results, while with 6 windows, WHAM, UI, and MBAR all fail to converge due to the lack of sufficient overlap between windows. On the other hand, the VFEP approach, both with spline (MLE-S) and rational interpolation (MLE-R) functions gives very good results for 11 windows compared to the 21 window results, and gives qualitatively correct results with only 6 windows.