In Eq. 8, ln γ r→z (r) represents the log volume change associated with transforming r to z, as illustrated in Fig. . . Defining the generalized work function ϕ = βU +ln (q), one can use the two-state BAR equation (extensively discussed in Ref. ) to estimate absolute FE of each macrostate corresponding to a polymorph. Here, one of the two datasets fed into the BAR algorithm is sampled from the PGM mode. At the same time, the other originates from the MD data that samples the equilibrium distribution of a given macrostate. Ergodic samples from the model distribution q were obtained by sampling the (uniform) base distribution p 0 and then transforming them via the learned map. Ensemble averages over MD data (⟨•⟩ p ) were instead evaluated on locally ergodic configurations, exclusively extracted from the validation dataset (i.e., data not included in the PGM training set). As such, we refer to this estimator as BAR V and indicate the absolute free energy estimates in reduced units obtained from this estimator as f BAR V crys , where the subscript crys indicates the polymorph.