Table 2. Statistical Metrics Used to Evaluate the Accuracy of Binding Free Energies Calculated for the PAK Data Set^a.

force field	MUE [kJ mol–1]	RMSE [kJ mol–1]	Kendall τ	Spearman ρ
GAFF	1.9 [1.80–2.01]	3.3 [3.14–3.50]	0.4 [0.33–0.46]	0.5 [0.45–0.60]
OpenFF	2.8 [2.66–2.89]	5.8 [5.62–6.00]	0.6 [0.57–0.65]	0.7 [0.71–0.76]
null model	2.1	3.7	0	0

^aMUE and correlation metrics (τ and ρ) relate to absolute binding free energies, whereas RMSE corresponds to all pairwise relative binding free energies. Numbers reported correspond to the mean, with upper and lower bounds of the 95% confidence interval in square brackets.