Elastic parameters of paramagnetic iron-based alloys from first-principles calculations

The elastic properties of paramagnetic (PM) Fe _1-xM _x (M = Al, Si, V, Cr, Mn, Co, Ni, and Rh; 0 ≤ x ≤ 0.1) solid solutions in the body-centered-cubic (bcc) and face-centered-cubic (fcc) structures are investigated using the exact muffin-tin orbital density functional method in combination with the coherent-potential approximation and disordered local-magnetic-moment model. All impurities considered here enlarge or leave nearly constant the equilibrium volume of PM Fe but at the same time produce both positive and negative changes in the elastic parameters. Some of the alloying elements induce opposite effects on shear elastic parameters C ^′ and C ₄₄ of PM bcc and fcc Fe, which is discussed. With a few exceptions, we find that the alloying effects on PM bcc Fe are smaller than on PM fcc Fe. The trends in the tetragonal elastic constant C ^′ show a general correlation with the trends obtained for the bcc-fcc lattice energy difference.