ELASTIC PROPERTIES OF NISI2, COSI2, AND FESI2 BY TIGHT-BINDING CALCULATIONS

In a semiempirical tight-binding scheme we calculate the total-energy curve for Ni, Fe, and Co disilicides in the CaF2 structure. Agreement with recent linear muffin-tin-orbital, total-energy calculations, to which the band structure has been fitted at high-symmetry points of the Brillouin zone, is very satisfactory. Special attention has been devoted to the form of the phenomenological repulsive potential, in order to include the anharmonic contributions. Elastic constants, frozen-phonon frequencies, and cubic anharmonicities at the GAMMA point are also estimated, in quite good agreement with the existing experimental data.