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An internally consistent thermodynamic data set has been derived utilizing results from all available experimental phase equilibria in a simultaneous iterative regression approach using 1/T vs. ln Kᵣₑd plots. Simultaneous evaluation of all reactions allows the extraction of an internally consistent data set of #DELTA#fH and S values with V0, cP, #alpha# and #beta# otherwise constrained. An objective function has been defined which requires maximum consistency with available experimental results and minimum deviation from available calorimetric data. One advantage of this procedure is that all available experimental results, compatible or not, are always visible during the calculations. Over 5300 experimental results from 244 contributions for 253 reactions involving 94 phase components have been used. The extracted data set reproduces 92% of the available phase equilibria experiments reported in the literature. It can be shown that for some phases the configurational entropy must be considered (e. g. CaAl-pyroxene, clinochlore, mullite, phlogopite). With the addition of a configurational entropy for these phases the reproduction of the available experimental results is significantly improved. The configurational entropy for these phases is chiefly responsible for the observed differences between this and other available internally consistent data sets. In these other data sets non-addition of configurational entropy for these phases is compensated for by adjustments in the enthalpy and/or in other refined thermophysical parameters such as heat capacities. The configurational entropies used here are quite straightforward and involve mostly tetrahedral Si/Al and octahedral Mg/Al disorder. (orig. )
Matthias Gottschalk (Mon,) studied this question.