Structural stability, site preference and lattice vibrations of RFe12−xTax (R = Tb, Dy, Ho)

An investigation of the structural and vibrational properties of RFe12−xTax (R = Tb, Dy, Ho) compounds has been performed by a series of interatomic pair potentials obtained through the lattice inversion method. Calculated results show Ta atoms can stabilize RFe12−xTax with ThMn12-type structure, and Ta atoms substitute for Fe with a strong preference for the 8i sites. The phase stability of the intermetallics RFe12−xTax is tested by many means including random atom shift, global deformation and high temperature disturbance under the control of the pair potentials. The calculated lattice parameters are corresponding to the experimental results. In particular, the phonon densities of states for RFe11.5Ta0.5 are first evaluated. A qualitative analysis is carried out with the relevant potentials for the vibrational modes, which makes it possible to predict some properties related to lattice vibration.