LATTICE-DYNAMICS OF TRANSITION-METAL DISILICIDES

NbSi2, TaSi2 and VSi2 phonon properties have been investigated at 300 K using inelastic neutron scattering and Raman scattering. The results are reported and compared to previous results obtained by other techn iques such as point-contact spectroscopy. Inelastic neutron scattering on powders allowed us to separate longitudinal and transverse acousti c from optical modes, especially for TaSi2 and NbSi2. The acoustic mod es are shifted towards higher energy when decreasing the molar mass of the compound. Triple axis inelastic neutron scattering on NbSi2 singl e crystal led to more detailed information about the phonon spectrum. The energy of most of the modes has been followed all along the first Brillouin zone. Raman scattering measurements carried out on NbSi2 sin gle crystals allowed us to obtain the energy at the Brillouin zone cen ter and the symmetry assignment of all the Raman active modes.