NEQ switching simulations are a reliable approach to converge free energy estimates between MM and ANI-2x Compared to the FEP results, the free energy estimates obtained from unidirectional and bidirectional NEQ work simulations are mostly in excellent agreement with the results obtained from the MFES shown in Figure . The single exception is hp19. For bidirectional NEQ, the 5 and 10 ps switching protocols give results that deviate from the MFES reference value by slightly more than 1 k B T (see also Tables and). None of this molecule's unidirectional NEQ results lie within the ± 1 k B T threshold, except for the 20 and 50 ps NNP→MM estimate. Particularly in the MM→NNP direction, the deviations are sizable. While except for hp19 all bidirectional NEQ results are extremely close to the MFES reference result, some unidirectional results deviate slightly but discernibly. In particular, this is the case for hp7, hp9 and hp18. In the MM→NNP direction, all deviations are within the ± 1 k B T threshold; the NNP→MM result for hp9 with the 5 ps switching protocol deviates by 1.02 k B T (see Table ).