CALPHAD modeling based on Gibbs energy functions from zero kevin and improved magnetic model: A case study on the Cr–Ni system

Liu, Hao; Ruban, Andrei V.

doi:10.1016/j.calphad.2021.102268

Cited by 11 publications

(4 citation statements)

References 147 publications

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“…One can expect that models applied to metals can be extended to the molten salt systems, especially much of the ongoing atomistic modeling of molten salt systems can further support such a CALPHAD modeling effort when experiments are challenging to perform. Recently, efforts have been made on improving the descriptions of pure elements [33][34][35][36] be more accurate in both low temperatures down to zero Kelvin and high temperatures above melting point and is highly desirable to apply the same approach for the description of unary substances.…”

Section: Suggestions On Improving Thermodynamic Modeling Of Molten Saltsmentioning

confidence: 99%

Fundamental Issues Identified for Thermodynamic Description of Molten Salt Systems

Liu

2022

J. Phase Equilib. Diffus.

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Thermodynamic modeling of the molten salt systems is critical in the design of advanced nuclear power plants, materials recycling, and many other important clean energy applications. As one of the most capable computational thermodynamic approaches, the CALPHAD (Calculation of Phase Diagrams) method has been widely used for multicomponent thermodynamic database development and further support more physics-based modeling. Although considerable CALPHAD modeling efforts for molten salt systems have been made, we found that no evaluation has been performed regarding the unary thermodynamic models for the molten salt systems despite the fact that more than one pure substance database is available for the CALPHAD modeling. Therefore, the thermodynamic descriptions of the pure salts should be critically evaluated to ensure a high-fidelity molten salt thermodynamic database. In this work, we comprehensively analyzed some selected molten salts using different available thermodynamic descriptions from two databases as an example. One is the SSUB database released by the SGTE (Scientific Group Thermodata Europe), and the other is the FactPS database from the FactSage. The significant discrepancies observed in the thermodynamic description between the existing CALPHAD pure substance databases and experiments call for an urgent effort to improve.

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Section: Suggestions On Improving Thermodynamic Modeling Of Molten Saltsmentioning

confidence: 99%

Fundamental Issues Identified for Thermodynamic Description of Molten Salt Systems

Liu

2022

J. Phase Equilib. Diffus.

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“…M (T, B) is the spontaneous magnetization (B = 0) and the magnetic-filed-induced magnetization (B ̸ = 0) which is originated from the classical Weiss molecular field theory [38][39][40] (supplementary note 1). When the Gibbs free energy of ferromagnetic state has been chosen as the reference state, the G intrinsic-mag (T, B) can be expressed as [7,19,41]:…”

Section: Intrinsic Magnetic and Magnetic-field-induced Gibbs Free Energymentioning

confidence: 99%

New evaluation of the thermodynamics stability for bcc-Fe

Liang

Hou

Zhang

et al. 2022

J. Phys.: Condens. Matter

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The thermodynamic properties for bcc-Fe were predicted by combination of the first-principles calculations, the quasiharmonic approximation, the CALPHAD method and the Weiss molecular field theory. The hybrid method considers the effects of the lattice vibration, electron, intrinsic magnetism and external magnetic fields on the thermodynamic properties at finite temperature. Combined with experimental data, the calculated heat capacity without external magnetic fields was used to verify the validity of the hybrid method. Close to the Fermi level the high electronic DOS leads to a significant electronic contribution to free energy. Near the Curie temperature lattice vibrations dominant the Gibbs free energy. The order of the other three excitation contributions to Gibbs free energy from high to low is: intrinsic magnetism > electron > external magnetic fields. The investigation suggests that all the excitation contributions to Gibbs free energy are not negligible which provides a correct direction for tuning the thermodynamic properties for Fe-based alloy.

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“…In recent decades, Ni-Cr alloys have been studied using both experiment and theory, however, an accurate quantitative understanding of their thermodynamic and electrochemical behaviors is still limited. For the thermodynamic stability of Ni-Cr alloys, their free energies of formation (Δ f G) were obtained in previous theoretical studies by fitting the experimentally determined phase boundaries [26][27][28][29] . To establish a deeper thermodynamic understanding, it is still desirable to accurately deterimine the individual contributions of different components (e.g., electronic energy, vibrational free energy, and configurational entropy) in those fitted Δ f G values.…”

Section: Introductionmentioning

confidence: 99%

Elemental partitioning and corrosion resistance of Ni–Cr alloys revealed by accurate ab-initio thermodynamic and electrochemical calculations

Huang,

Xie,

Sieradzki

et al. 2023

npj Mater Degrad

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Elemental partitioning during thermal processing can significantly affect the corrosion resistance of bulk alloys operating in aggressive electrochemical environments, for which, despite decades of experimental and theoretical studies, the thermodynamic and electrochemical mechanisms still lack accurate quantitative descriptions. Here, we formulate an ab initio thermodynamic model to obtain the composition- and temperature-dependent free energies of formation (ΔfG) for Ni–Cr alloys, a prototypical group of corrosion-resistant metals, and discover two equilibrium states that produce the driving forces for the elemental partitioning in Ni–Cr. The results are in quantitative agreement with the experimental studies on the thermodynamic stability of Ni–Cr. We further construct electrochemical (potential–pH) diagrams by obtaining the required ΔfG values of native oxides and (oxy)hydroxides using high-fidelity ab-initio calculations that include exact electronic exchange and phononic contributions. We then analyze the passivation and electrochemical trends of Ni–Cr alloys, which closely explain various oxide-film growth and corrosion behaviors observed on alloy surfaces. We finally determine the optimal Cr content range of 14–34 at%, which provides the Ni–Cr alloys with both the preferred heat-treatment stability and superior corrosion resistance. We conclude by discussing the consequences of these findings on other Ni–Cr alloys with more complex additives, which can guide the further optimization of industrial Ni–Cr-based alloys.

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CALPHAD modeling based on Gibbs energy functions from zero kevin and improved magnetic model: A case study on the Cr–Ni system

Cited by 11 publications

References 147 publications

Fundamental Issues Identified for Thermodynamic Description of Molten Salt Systems

Fundamental Issues Identified for Thermodynamic Description of Molten Salt Systems

New evaluation of the thermodynamics stability for bcc-Fe

Elemental partitioning and corrosion resistance of Ni–Cr alloys revealed by accurate ab-initio thermodynamic and electrochemical calculations

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