Phonon dispersion relations of metallic NiSi2 and CoSi2 by semi-empirical tight-binding calculation

We report some preliminary results concerning the phonon dispersion relations and the density of states of NiSi2 and CoSi2 obtained with semi-empirical tight-binding calculations. In the nickel disilicide case we obtain a good agreement to the experimental disorder-activated Raman spectrum. For CoSi2 we point out that the independent behavior of the acoustic dispersion relations with respect to the optical branches, formerly predicted on the basis of neutron scattering data, does not match with the low-frequency position of Raman and infrared modes, very recently observed and confirmed by ab-initio calculations.