Critical assessment of three kinds of activity coefficients of carbon and related mixing thermodynamic functions of Fe–C binary melts based on atom–molecule coexistence theory

Raoultian activity coefficients γ_C^0 of C in infinitely dilute Fe–C binary melts at temperatures of 1833, 1873, 1923, and 1973 K have been determined from the converted mass action concentrations N_C^' of C in Fe–C binary melts by the developed AMCT- N i model based on the atom–molecule coexistence theory (AMCT). The obtained expression of γ_C^0 by the developed AMCT- N i model has been evaluated to be accurate based on the reported ones from the literature. Meanwhile, three activity coefficients γ_C , f_%, C , and f_H, C of C coupled with activity a_R, C or a_%, C or a_H, C have been obtained by the developed AMCT- N i model and assessed through comparing with the predicted ones by other models from the literature. The first-order activity interaction coefficients ε_C^C , e_C^C , and h_C^C related to γ_C , f_%, C , and f_H, C are also determined and assessed in comparison with the reported ones from the literature. Furthermore, the integral molar mixing thermodynamic functions such as Δ_mix H_m, Fe - C , Δ_mix S_m, Fe - C , and Δ_mix G_m, Fe - C of Fe–C binary melts over a temperature range from 1833 to 1973 K have been determined and evaluated to be valid based on the determined ones from the literature.