Local-field correction in the lattice dynamics of b.b.c. transition metals

Summary

It is shown that the off-diagonal components of the inverse dielectric matrix which determine the local-field correction associated with s-d interactions, make contributions to the dynamical matrix for phonon dispersion in the body-centred cubic transition metals V, Nb and Ta which tend to cancel the Born-Mayer contribution, just as the diagonal components of the inverse dielectric matrix tend to cancel or screen the long-range (Coulombic) contribution. Numerical calculations show that the can-cellation of the Born-Mayer contribution to the dynamical matrix by the local-field correction is such that the effective short-range interatomic potential turns out to be attractive rather than repulsive in these metals and accounts for some peculiar shapes of the major soft modes observed in these metals.