Fig. 6: Alchemical free energy simulations. | Nature Communications

Fig. 6: Alchemical free energy simulations.

From: Interpolation and differentiation of alchemical degrees of freedom in machine learning interatomic potentials

Fig. 6

a The thermodynamic cycle considered in this work, consisting of perovskite (P) and non-perovskite (N) phases of CsPbI3 and CsSnI3. ΔG values are labeled by phase (P or N) and composition; for instance, ΔGN,Pb→Sn indicates the gibbs free energy change for the non-perovskite phase from CsPbI3 to CsSnI3. b Upper panel: the alchemical free energy of Pb→Sn conversion in both phases, plotted against the simulation temperature. Lower panel: the ΔΔG values in Eq. (13) computed from the results in the upper panel. The deviations between the two methods at lower temperatures result from the phase transformation between the perovskite phases. c Statistical efficiency for the Frenkel–Ladd paths and alchemical path of CsPbI3 to CsSnI3 transformation for P phase, plotted against the switching time. Upper panel shows the deviation of Gibbs free energy from the reference value at the longest switching time (60 ps), and the lower panel shows average dissipated energies (Eq. (10)). For panels b and c, each data point represents the average of four statistically independent simulations, with standard deviations shown as error bars. Source data are provided as a Source Data file.

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