Therefore, to validate our model with respect to experimental results, we compute the B2 coefficients of the most accurate model 5 and compare it to the experimental reference (see Figure ). With NQE incorporated using PIMD, the computed B2 agree well with the experimental data, and the errors are within the statistical uncertainties among different ML fittings. This test provides a direct proof to the accuracy of our model in dimer interactions, with only 1421 dimer geometries included in the training set. of the H atoms are considered to be quantum in nature. This finding is different to the previously reported MB-pol results, 134 but is consistent with other existing studies. It is indicated that the magnitude of NQE in RDFs is more force-field-dependent than one may expect, and explicit quantum simulations are essential in the validation of ab initio force field.