Effect of the order on the structural and magnetic properties of Fe-X (X=Al, Si) alloys with B2 structure

Previous ab initio super-cell calculations of the magnetic properties of th e ordered Fe1-xAlx alloy in the B2 structure are extended to include the di sordered state of the alloy and completed with the calculations for ordered and disordered Fe1-xSix alloys. The configurations of the Fe atoms in the anti-site (AS) positions of Fe-X super-cell with the antiferromagnetic orde r were found. The ground state of Fe1-xAlx with x similar or equal to 0.3 s hows the antiferromagnetic order of the Fe-AS magnetic moments. The concent ration dependence of the equilibrium lattice parameter and magnetic moment of Fe1-xXx in the ordered and disordered state differ qualitatively.