  Ab initio calculations and a direct method are applied to derive the phonon
dispersion relations and phonon density of states for the ZrC crystal. The
results are in good agreement with neutron scattering data. The force constants
are determined from the Hellmann-Feynman forces induced by atomic displacements
in a 2x2x2 supercell. The elastic constants are found using the deformation
method and successfully compare with experimental data.
