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Abstract

Novel physically-based description of thermodynamic properties from 0K up to 6000K has been derived in this work. The proposed model is a flexible extension of the segmented regression (SR) covering temperatures from 0K up to the melting point [1] to the high temperatures far above the melting point. It contains five model parameters to be estimated from experimental / DFT data, same as in original SR formulation and it enables the modification of the melting point value without the need for additional re-assessments, e.g., in case of pure chromium where the correct value of melting point is still under discussion.

The modified SR model has been successfully applied for the description of thermos-physical properties of eight transition elements, such as Ti, V, Ni, Fe, Mn, Cr, Nb and Mo. In all considered cases it shows a good agreement with available experiments. To estimate the accuracy of newly proposed SR model, a comprehensive review of recommended values for heat capacities, relative enthalpies, standard entropy, melting and Debye temperatures has been performed. The model performance has been evaluated in comparison to the existing alternative physically-based description valid from 0K [2-4].

References
[1] Roslyakova, I., et al. Modeling of Gibbs energies of pure elements down to 0K using segmented regression, CALPHAD, 55 (2016).
[2] Desai, P.D. Thermodynamic properties of vanadium. International Journal of Thermophysics (1986).
[3] Thurnay, K. Thermal properties of transition metals. Forschungszentrum Karlsruhe GmbH Technik und Umwelt (Germany). Inst. fuer Neutronenphysik und Reaktortechnik (1998).
[4] Bigdeli, S. et al. On the third‐generation CALPHAD databases: An updated description of Mn., Physica Status Solidi (b) 252.10 (2015): 2199-2208.