Lattice dynamics inZrB12andLuB12:Ab initiocalculations and inelastic neutron scattering measurements

Abstract

The first ab initio calculations using ultrasoft pseudopotentials within the local-density approximation in superconducting ${\text{ZrB}}_{12}$ are reported, together with an inelastic neutron scattering study of its lattice dynamics. As in previously studied rare-earth dodecaborides, the phonon spectra are mainly determined by vibrations of the rigid boron network whereas Zr atoms vibrations have a quasilocal character and are localized in a narrow energy range around $E\ensuremath{\approx}17\text{ }\text{meV}$. The results consistently indicate that the phonon modes corresponding to Zr vibrations are responsible for a considerable electron-phonon interaction and could take part in the formation of the superconducting state below ${T}_{c}\ensuremath{\approx}6\text{ }\text{K}$ as was suggested previously.