Hillert Materials Modeling Colloquium series IV: The Equi Entropy Criterion (EEC) for the 3rd generation unary database

The properties of solid phases of the elements far above their melting temperatures is important for thermodynamic calculations because in alloys an element may dissolve in various solid phases far above its melting temperature.

In the SGTE 1991 unary database the heat capacity of the stable solid phase of an element had a breakpoint at the melting T and at higher T the heat capacity of the solid was forced to approach that of the liquid phase. Without this breakpoint the heat capacity of the metastable solid may increase rapidly and its entropy becomes larger than that of the liquid and the solid may become stable again at high T.

Various physical phenomena have been proposed to handle this problem and the final decision is to implement in the thermodynamic software a check preventing a solid phase with higher entropy than the liquid at the same T to be stable. This is called the Equi Entropy Criterion (EEC).

B Sundman, U R Kattner, M Hillert, M Selleby, J Ågren, S Bigdeli, Q Chen, A Dinsdale, B Hallstedt, A Khvan, H Mao, R Otis, A method for handling the extrapolation of solid crystalline phases to temperatures far above their melting point, Calphad (2020) 101737

Lecturer

Bo Sundman got his PhD in 1981 with Mats Hillert. Together with John Ågren, Bo Jansson and other PhD students for Mats, he created Thermo-Calc. During the CAMPADA consortium 1990–2000 “Stiftelsen för Tillämpad Termodynamik” was created as owner of the software and started Thermo Calc Software AB in 1997.

Bo Sundman's interest is to develop and implement models and assess systems for multicomponent thermodynamic databases. In 2012, Bo Sundman retired and to continue modeling he began writing a free thermodynamic software, OpenCalphad. He participated in the development of the SGTE unary database in 1991 and he is now assisting Malin Selleby with the 3rd generation unary database.

Bo Sundman has published more than 180 papers and received the Calphad ”Triangle” Award 2002, a Humboldt senior researcher award from Germany in 2012 and the NIMS Award in Japan
2017. Together with Dr Leo Lukas and Dr Suzana G Fries, he has written the book "Computational Thermodynamics, the Calphad Method" published by Cambridge University press in 2007.

Hillert Materials Modeling Colloquium Series is arranged by Hillert Modeling Laboratory
Department of Materials Science and Engineering
KTH Royal Institute of Technology

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