Sign of the interaction parameter in disordered Fe-Al alloys

In the framework of the coherent potential approximation we show that the interaction parameter for disordered Fe-Al alloy strongly depends on the concentration. The calculations were provided within linear muffin-tin orbital formalism in the atomic sphere approximation. Calculation data for B2 phase for different concentrations were used to extract the interaction parameter, V(0), for disordered solid solutions and were compared with the parameter treated from the X-ray scattering data. The concentration dependence of 7(0) leads to the failure of the application of the regular solid solution model to the study of the phase relations in the Fe-Al system. Parameter V(k_s), which is responsible for ordering tendency, also depends on concentration, and it is in accordance with the experimental data.