The scalpha and scbeta parameters, which control the softness of the potential, were set to 0.5 and 12 Å 2 , respectively, as in previous work . To avoid any Hamiltonian lag , energy minimization, heating, density equilibration, NPT preproduction equilibration, and NPT production dynamics were all carried out with potential energy functions corresponding to the λ) of a -value of every λ) of a -window. Hydration free energies, error estimates, and convergence metrics were computed from the decorrelated dV/dl values (the derivative of the potential with respect to λ) of a ) from the Amber output files with the alchemlyb 91 TI estimator.