Fig. 4

 Comparison of − values from experiment and − values from the simulations based on the initial CHARMM parameter set (blue symbols in y-axis range from 6 to 11 kcal/mol) and the final tuned IFF parameter set (green symbols, all within about 0.5 kcal/mol from the experimental values). The solid black line represents perfect agreement between simulation and experimental values of adsorption free energy. The dashed red lines represent deviations of ±1.0 kcal/mole around the solid black line, which we designated as the maximum tolerable deviation from the experimental values