Figure 4(d) yields the latent heat and the entropy of fusion, 4.505kJ=mol and 17.46 J=molK, respectively, previously estimated as 4.39 kJ=mol and 17.9 J=molK [19]. The Gibbs free-energy profile at Tm, GðHÞ¼H −TmSðHÞ, connecting the phases at enthalpies H1and H2, is shown in Fig. 4(e). The barrier height is estimated as 0.27 kJ=mol. If we take T as the control variable, the Gibbs free energy, now evaluated as HðTSÞ−TSSðTSÞ, is triple valued in the coexistence regime, with equilibrium corresponding to the lowest branch and the transition at the crossing of the two lower branches (Fig. 5). Clearly, using enthalpy as the control variable gives a simpler description.