Vibrational properties of Pd1-cFec disordered binary alloys

The transition metal model potential of Animalu is applied to study the lattice dynamics of two f.c.c. disordered alloys of Pd and Fe, namely Pd0.96Fe0.04 and Pd0.90Fe0.10. First the model potential is used to compute the radial and tangential force constants of Pd and Fe for the two alloys and also those of pure Pd up to ten sets of nearest neighbours. The concentration average of these force constants is used to determine the force constants of the two disordered alloys. Next, the dynamical matrix is constructed and the secular equation is solved to calculate the phonon dispersion curves and elastic constants of pure Pd and Pd0.96Fe0.04 and Pd0.90Fe0.10 alloys. In all the cases a reasonably good agreement is found between the computed and experimental results, when three-body forces are incorporated in the interaction system. Phonon density of states and the temperature dependence of specific heat and Debye temperature of the two alloy systems are also computed and presented. (orig.)