Investigation of structural imitation and lattice vibrations of Pr2Fe17−xMnx compounds

We have investigated the structural properties of Pr2Fe17−xMnx compounds by using quasi-ab initio pair potentials ΦFe-Fe(r), ΦPr-Fe(r), ΦPr-Pr(r), ΦPr-Mn(r), ΦFe-Mn(r) and ΦMn-Mn(r). In Pr2Fe17-xMnx, the ternary elements Mn substitute for Fe atoms without changing the crystal structure. The calculated cohesive energy curves show that for all values of x, Mn preferentially substitutes for Fe in the 6c site and randomly substitutes for Fe in the 18f and 18h site. The calculated lattice constants coincide quite well with experimental values. Furthermore, the phonon density, specific heat and vibrational entropy of these compounds are also calculated. It is interesting that simple pair potentials can describe these extremely anisotropic materials.