Figure : Correlations between unsigned error (UE) and overlap coefficient for various transition lengths in case of the NEQ method. "600 ps" denotes the recommended standard protocol, whereas "Apo" denotes the same protocol but using apo structures at λ = 0 end-point. Pearson's r is shown in the inset. Weak anti-correlations in most cases emphasise the necessity of non-zero overlap for unbiased ABFE predictions. The majority of cases with large UEs have zero overlap.