Atomistic simulation of the structure and Curie temperature of R2(Co, Ti)17 (R=Pr, Nd, Sm, Gd, Tb and Dy) and R2(Co, Ti)17Cx

An atomistic study is presented on the phase stability, site preference and lattice constants of the Co-rich rare-earth intermetallic compounds R2(Co, Ti)17 (R=Pr, Nd, Sm, Gd, Tb and Dy) and R2(Co, Ti)17Cx. The space group remains unchanged upon substitution of Ti for Co in R2(Co, Ti)17 and the calculated structural parameters correspond well to experimental data. The site preference of Ti atoms at Co sites is also evaluated and the order is given as 6c, 18f, 18h and 9d for the rhombohedral Th2Zn17-type structure, and 4f, 12j, 12k and 6g for the hexagonal Th2Ni17-type structure. The effect of interstitial C atoms in R2(Co, Ti)17Cx on the structural properties is also studied. In addition, the decrease of the Curie temperature Tc with increasing Ti concentration is explained qualitatively by the exchange-interaction model.