The condition χ 2 4Pχ 2 LS2 < -0.002 was used to pick the fitting model, where χ 2 LS2 and χ 2 4P denote to the χ 2 values resulting from fitting equations 7 and 17, respectively, to the TCFs. This condition is somewhat arbitrary but does not have a substantial impact because the parameters obtained with the LS2 and 4P models are very similar, as shown below. The uncertainty in ∆C int was estimated from the standard deviation of the MD trajectory chunks that were used for the fitting of C int .