Electronic structure, ordering effects, phase stability, and magnetism in ${\mathrm{Fe}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Cr}}_{\mathit{x}}$ systems

The total energies and magnetic properties of ideally ordered bcc Fe-Cr compounds and random substitutional disordered bcc ${\mathrm{Fe}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Cr}}_{\mathit{x}}$ alloys are calculated using spin-polarized, self-consistent linear-muffin-tin-orbital-based methods. Calculated total energies are almost degenerate for magnetic and nonmagnetic states in ${\mathrm{FeCr}}_3$, which is favorable for the Invar effect. Comparison with the results for complete disorder and with the total energies of the pure elements, lead to the conclusion that disordered states in the form of clusters, are stable at most concentrations. The effect of order is also crucial for the FeCr composition, where the CsCl structure gives ferromagnetic Cr moments, in contrast to the antiferromagnetic configurations in most other cases.