Figure 1. Solvation free energy of anthracene molecule.
The simulations were performed in boxes of 6 different sizes (A). We repeated the calculation 20 times for each simulation box. The outcome of each calculation is depicted as an orange circle in panels B and C. (B) Averages over 20 simulations together with the associated 95% confidence intervals reveal that there is no box size dependence for the solvation free energy (left panel). Three unlikely, yet possible, scenarios are depicted in the middle panel, where results from only one calculation per simulation box are considered. Given this insufficient (N = 1) sampling of solvation free energies, we could reach a false conclusion that the values increase, decrease or increase and then decrease with a larger simulation box. The right panel shows the same trends as in the middle panel, but the estimates have their 95% confidence intervals depicted as well: considering the statistical uncertainty illustrates that all the trends in terms of box size dependence based on anecdotal evidence are not statistically significant.