First-principles Calculations For Elastic Properties And Electronic Structures Of Fe-based Alloys

Compared to giant magnetostricitive alloys with rare earth, Fe-based magnetostrictive alloys are cheaper and their saturation field is lower. Once appeared, they attract much attention. The first-principles method is used to calculate elastic constants, elastic modulus and electronic structures of Fe-based alloys. The effect of dopant in Fe-based alloys on elastic properties is studied in theory.The elastic properties of Fe16-xAlx alloys with cubic structure were studied. The optimized lattice constants agree well with the experimental value. The value of elastic modulus in Fe Al is larger than that of pure Fe. However, with the increasing of Al atom concentration, polycrystal bulk modulus increases, whereas young’s modulus and shear modulus decrease obviously. The decrease of C11-C12 is conducived to improving the magnetostriction coefficient λ100.The elastic properties of Fe16-xGax alloys were calculated. Ga doping has the same effect as Al doping. The value of C11-C12 in Fe Ga alloys with cubic structure reduces with the increasing of Ga atom concentration. It changes from 115 GPa in Fe15 Ga to 40 GPa in Fe12Ga4. In addition, the structure of Fe12Ga4 changes from cubic phase into tetragonal phase when there are Ga-Ga atom pairs. The lattice constant increases along the direction with Ga atom pairs and decreases along the direction perpendicular to Ga-Ga atom pairs. It is found that the elastic modulus is softened along the direction with Ga-Ga atom pairs.The effect of FeAl and FeGa doped with Cr and rare earth atoms on elastic modulus and electronic structures were studied. It is found that young’s modulus and shear modulus increase when FeAl and FeGa alloys doped with Cr. However, all the elastic modulus decrease dramaticlly when doped Fe Al and FeGa alloys with rare earth atoms. For Fe12Al4,Ce doping is the most conducive to softening elastic modulus. And for Fe12Ga4, Tb doping is the most conducive to softening elastic modulus.