Structural and thermodynamic properties of Fe based compounds with NaZn13-type

A series of Fe based compounds with NaZn13-type structure is studied by using inversed interatomic potentials. Calculated results show that Si atoms and Co atoms are preferentially substituted for Fe atoms at 96i site. The addition of Si or Co makes the cohesive energy decrease. It is found that the lattice constants of LaFe13-x-yCoySix and NdFe13-x-yCoy Six decrease with the increase of Co content. The investigation on the phonon density of states indicates that the lower frequency modes are mostly excited by the rare-earth atoms, and the higher frequency modes are mostly excited by Si atoms. Moreover, the addition of Co atoms makes the Debye temperature of LaFe11.5-yCoySi1.5 compounds increase.