Theoretical study on the phase stability, site preference, and lattice parameters for Gd(Fe,T)12

The stability of the intermetallics Gd(Fe, T)(12) and the site preferences of the ternary 3d or 4d transition element T are investigated by using a series of interatomic pair potentials, Phi (Fe-Fe)(r), Phi (Fe-Gd)(r), Phi (Fe-T)(r), Phi (T-T)(r), Phi (T-Gd)(r), and Phi (Gd-Gd)(r), for the first time. The calculated results show that adding either Cr, Mo, Ti, or V atoms makes the crystal cohesive energy of Gd(Fe, T)(12) decrease markedly, proving that these atoms can stabilize Gd(Fe, T)(12) with ThMn12 structure even though the GdFe12 crystal structure is itself metastable. The calculated lattice parameters are in good agreement with experiment. The amount of cohesive energy decrease is correlated with the species and occupation site of the ternary atoms. The order of site preference of these stabilizing elements T is 8i, 8j, and 8f, with 8i corresponding to the greatest energy decrease. The calculated results further show that the addition of Co, Cu, Ni, Sc, and Zn does not stabilize the GdFe12 phase in the ThMn12 structure. The calculated results reported correspond well to available experimental data indicating that the ab initio interatomic potentials can be used to describe rare-earth materials.