Representation Reaction Abilities of Structural Units and Related Thermodynamic Properties in Fe– P Binary Melts Based on the Atom– M olecule Coexistence Theory

A thermodynamic model for calculating the mass action concentrations of structural units in Fe–P binary melts based on the atom–molecule coexistence theory, i.e., AMCT– N i model, has been developed and verified through comparing with the reported activities of both P and Fe in Fe–P binary melts with mole fraction x P of P <0.33 in a temperature from 1406 K to 1973 K. The calculated mass action concentration N P of P or N Fe of Fe has a very good 1:1 corresponding relationship with the reported activity a R,P of P or a R,Fe of Fe relative to pure liquid P(l) or Fe(l) as standard state, and can be applied to substitute the measured activity a R,P of P or a R,Fe of Fe in Fe–P binary melts. The Raoultian activity coefficientγ P 0of P andγ Fe 0of Fe in the infinitely dilute solution of Fe–P binary melts in a temperature from 1406 K to 1973 K have been determined from the calculated mass action concentrations N i of structural units in Fe–P binary melts. The activity a R, i , a %, i , and a H, i of P or Fe relative to three standard states have been obtained. The values of the first‐order activity interaction coefficientϵ i iore i iorh i iof P and Fe related with activity coefficients γ i or f %, i or f H, i of P and Fe in Fe–P binary melts are also determined.