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How are diagrams such as above plotted? Since empirical studies are slightly off from the 'ideal', what is the source for the phase plots?

Layman
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    That particular diagram is from Thermo-Calc (https://www.thermocalc.com/ - the triangle symbol in the lower left indicates the program). Thermo-Calc implements thermodynamic models based on Calphad (Calculation of Phase Diagram) principles. One selects appropriate models for the Gibbs free energy of the phases, takes the known experimental data, and fits parameters of the model such that the calculations 'best fit' the data. There is a journal named Calphad which has a lot of literature (and other journals) and several books and conferences on the topic. – Jon Custer Jul 02 '19 at 21:29
  • I see. Are models on it citable or is it more of a toy-model deal? – Layman Jul 02 '19 at 22:19
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    Searching Web of Science for topic "Calphad" results in 3202 results. It is a (growing) field of materials science, with many applications. There is a lot of good thermodynamics, crystal structure, and more applications of first-principle (e.g. DFT) to get at relevant thermodynamic parameters. So, no, it is not a toy model thing (or hasn't been for the past 30 year or so). I have several answers on Chemistry that use Calphad results to explain what is going on in binary phase diagrams. – Jon Custer Jul 02 '19 at 22:24
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    https://chemistry.stackexchange.com/questions/19454/boundary-lines-in-phase-diagrams-and-the-lever-rule/19468#19468 might help visualize how the set of Gibbs free energy curves of the various phases ends up in a binary phase diagram. – Jon Custer Jul 02 '19 at 23:04
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    For starters see: Clausius Claperon – A.K. Jul 03 '19 at 01:59

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