First-principles studies of the phase transitions in Fe-Si alloys

In this paper, the structural and magnetic properties of Fe$_{100-x}$Si$_{x}$ alloys ($10 \le x \le 25,0$ at.%) were calculated. The structural phase transition temperatures for the crystal structures A2, B2, and D03 were estimated from the geometry optimization. The Curie temperatures were calculated in a molecular-field approximation using the constants of magnetic exchange interaction calculated ab initio. For all the considered concentrations, with the temperature increase, we observed the structural transitions from the ordered cubic phase to a disordered structure, with the intermediate stage of a partially disordered state. The ferromagnet-paramagnet transition was observed for all the compositions, though in various crystal phases.