Ab initiolattice dynamics and electron-phonon coupling in the refractory compounds ZrN and HfN

We present a theoretical calculation of the phonon dispersions and electron-phonon coupling in the refractory compounds ZrN and HfN using modern ab initio techniques. We find very good agreement with high-precision tunneling measurements of the Eliashberg function for ZrN, thus resolving a longstanding contradiction with previous theoretical results. To clarify some qualitative differences in the dispersion of the optical branches between our results and available experimental data for ZrN, we have also performed a neutron-scattering measurement of the generalized phonon-density of states, which corroborated our theoretical findings.