The Calphad (Calculation of phase diagrams) technique has reached maturity. It is widely used to model thermodynamic properties for each phase and simulate multicomponent multi-phase behavior in complex systems. It started from a vision of combining data from thermodynamics, phase diagrams and atomistic properties such as magnetism into a unified and consistent methodology. It has become now a powerful method for a wide range of applications where modeled Gibbs energies and their derivatives are used to calculate properties and simulate phase transformations in real multicomponent materials. Diffusion and solidification simulations can be carried out by using the second derivatives of Gibbs energy and data from laboratory experiments such as rapid solidification process. Whenever the thermodynamic description of a system is required, the Calphad technique can be applied.

The successful use of Calphad in these applications relies on the development of multicomponent databases, which describe many different kinds of thermodynamic functions in a consistent way, all checked to be consistent with experimental data. The construction of these databases is still a very demanding task, requiring expertise and experience. Furthermore, the growing range of applications of these databases increases the feedback but also the demand for updates and improvements. The development of new models and the rapid advance of first-principles (Latin: ab-initio) calculations make the assessment techniques very dynamic and challenging.

The OpenCalphad project was initiated to create an open-source code implementing the Calphad technique.

In the present version, the code can read thermodynamic databases using the most popular “TDB” format. The software can perform equilibrium calculations for multicomponent systems and show several thermodynamic properties under different conditions. The Compound Energy Formalism (CEF) and the partially ionic 2-sublattice liquid (I2SL) models with magnetic contributions have been implemented and new models will be added in the future.

Publications about and related to OpenCalphad

H. L. Lukas, S. G. Fries and B. Sundman (2007). Computational Thermodynamics: The Calphad Method. Cambridge University Press, United Kingdom.

B Sundman, U R Kattner, M Palumbo and S G Fries, OpenCalphad - a free thermodynamic software, Integ Mat Manu Innov, (2015) 4:1

B Sundman, X-L Liu and H Ohtani, The implementation of an algorithm to calculate equilibria for multi-component systems with non-ideal phases in a free software, Comp Mat Sci, (2015), 211-137

B Sundman, U R Kattner, C Sigli, M Stratmann, R Le Tellier, M Palumbo and S G Fries, The OpenCalphad thermodynamic software interface, Comp Mat Sci, (2016), 188&-196

A van de Walle, R Sun, Q-J Hong and S Kadkhodaei, Software tools for high througput CALPHAD from first-principles data, Calphad, (2017), 70-81

B Sundman, Q Chen and Y Du, A review of Calphad Modeling of Ordered Phases, J Phase Equilib Diffus, (2018) 39:678-693

J Li, B Sundman, J G M Winkelman, A I Vakis and F Picchioni, Implementation of the UNIQUAC model in the OpenCalphad software, Fluid Phase Equil, (2020), 112398

J Herrnring, B Sundman and B Klusemann, Diffusion-driven microstructure evolution in OpenCalphad, Comp Mat Sci, (2020), 109-236

C Introini, J Sercombe and B Sundman, Development of a robust, accurate and efficient coupling between PLEIADES/ALCYONE 2.1 fuel performance code and the OpenCalphad thermo-chemical solver, Nucl Eng and Des, (2020) , 110818

K Samuelsson, J-C Dumas, B Sundman, J Lamontangne and C Gueneau, Simulation of the chemical state of high burnup (U,Pu)O2 fuel in fast reactors based on thermodynamic calculations, J Nucl Mat, (2020), 151969

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

Z He, B Kaplan, H Mao and M Selleby, The third generation Calphad description of Al-C including revisions of pure Al and C, Calphad, (2021) 102250

B Sundman, N Dupin and B Hallstedt, Algorithms useful for calculating multi-component equilibria, phase diagrams and other kinds of diagrams, Calphad, (2021) 102330

C Introini, J Sercombe, I Ramiere and R Le Tellier, Phase field modeling with the TAF-ID of inciplient melting and oxygen transport in nuclear fuel during power transients, J Nucl Mat, (2021)151173

J Herrnring, B Sundman, P Staron and B Klusemann, Modeling precipitation kinetics for multi-phase and multi-component system using particle size distributions via moving grid technique, Acta Mat, (2021) 117053