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Investigating the Al/Si mixed site occupancy in the β-AlFeSi phase

Paul Lafaye, Minh Duc Vo, Javier Jofré and Jean-Philippe Harvey

Article (2023)

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Abstract

This work investigates the mixed site occupancy of aluminium and silicon atoms in the β-AlFeSi phase. For this purpose, the six mixed Al/Si sites of the β-AlFeSi structure were considered independent and alternatively substituted by Al or Si, thus generating 64 ordered structures or end-members. The enthalpy of formation of each end-member was calculated by DFT. These calculations allowed us to derive the enthalpy of mixing of the solid solution at 0 K, over a wide range of chemical compositions, from the Al–Fe binary system to the Si–Fe binary system. In addition, the heat capacities of the solid solution were determined using a Debye model based on the calculation of the elastic constants and the equation of state of each end-member. These heat capacity values were used along with the enthalpy of formation we calculated to determine the Gibbs free energies of all the end-members of the β-AlFeSi structure. Finally, the configurational entropy of mixing from the Compound Energy Formalism (CEF) for the configurational entropy of mixing was subsequently used to calculate the occupation fractions of the Si sites on the Al sites of the β-AlFeSi structure, at 300 K and 938 K, the latter being the thermal decomposition temperature of this compound. These original site occupancy data were used to quantify the chemical ordering of the solid solution and to compare different sublattice (SL) models. We thus highlight that the SL model of the β-AlFeSi solution most commonly accepted in the literature generates considerable errors in its thermodynamic description, contrary to the model proposed in this paper, which is both simple and particularly accurate, consisting in merging the sites Al(1)–Al(6), the sites Al(2)–Al(3) as well as the sites Al(4)–Al(5).

Subjects: 1800 Chemical engineering > 1800 Chemical engineering
1800 Chemical engineering > 1804 Heat transfer
Department: Department of Chemical Engineering
Research Center: CRCT - Centre for Research in Computational Thermochemistry
Funders: CRSNG/NSERC Discovery Grant, Alliance Grant
Grant number: RGPIN-2017-06168, ALLRP 560998-20
PolyPublie URL: https://publications.polymtl.ca/54132/
Journal Title: Physical Chemistry Chemical Physics (vol. 25, no. 29)
Publisher: The Royal Society of Chemistry
DOI: 10.1039/d3cp01940c
Official URL: https://doi.org/10.1039/d3cp01940c
Date Deposited: 18 Jul 2023 12:02
Last Modified: 08 Apr 2024 18:12
Cite in APA 7: Lafaye, P., Vo, M. D., Jofré, J., & Harvey, J.-P. (2023). Investigating the Al/Si mixed site occupancy in the β-AlFeSi phase. Physical Chemistry Chemical Physics, 25(29), 20015-20025. https://doi.org/10.1039/d3cp01940c

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