Fig. 4.
Temperature dependence of tetrahedral entropy S Q(T) (A), defined in Eq. 11, (the red solid line is a guide to the eye) and tetrahedral specific heat C P Q = T(∂S Q/∂T)P (B), which has a maximum around the same temperature, T ≈ 250 ± 10 K ≈ T W, where the total specific heat C P Total has a maximum. Moreover, the difference ΔC P of the two specific heats is a constant within the error bars for all the temperatures, hence suggesting that C P Q is responsible for the Widom-line transformations.