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Ye et al. J Mater Inf 2023;3:15 https://dx.doi.org/10.20517/jmi.2023.08 Page 7 of 37

Where and present the Gibbs energy of pure Fe and RE in the structure of the solution phase φ,
[134]
and their values are obtained from the database . x and x are mole fractions of Fe and RE. R is the
FE
RE
universal gas constant, and T is the absolute temperature in Kelvin. The interaction parameters
are presented by two constants A and B , which are optimized. present the magnetic contribution
n
n
to the molar Gibbs energy of the of the solution phase φ. τ is expressed as , which is the
Curie temperature. Based on the proposed equation , g(τ) is expressed as:
[135]

in which p is a constant dependent on the structure of the solution phase φ (0.4 for the bcc phase and 0.28
for other phases).

Fe RE , Fe RE , Fe RE, and Fe RE, are considered to be stoichiometric compounds in the Fe-RE (RE = Tb,
6
23
2
3
2
17
Dy, Er, Lu, and Y) binary systems due to the lack of their composition range data. The heat capacities of
Fe Tb, Fe Er, Fe Dy, Fe Lu , Fe Lu, and Fe Y were experimentally determined by Germano and Butera ,
[99]
2
2
2
17 2
2
17
2
[113]
[125]
Tereshina et al. and Mandal et al. . In this work, according to available experimental data on heat
capacities, the Gibbs energies of Fe Tb, Fe Dy, Fe Er, Fe Lu, Fe Lu , and Fe Y were described by using a
2
2
2
17 2
17
2
2
thermodynamic model, which can establish well the heat capacities of intermetallic compounds from 0 K.
This model was employed in our previous assessments of Fe Ce and Fe Ce . The molar Gibbs energies of
[29]
2
2
17
these intermetallic compounds FeRE are presented as:
f
g
Where f and g are the stoichiometric numbers, and the parameters, A, B, C, and D, are to be assessed.