Ab initio phonon dynamics of iridium

Abstract

We present an investigation of the phonon spectrum of the transition metal iridium within the framework of a first-principles pseudopotential mixed-basis method. The full phonon spectrum is determined by means of a real-space approach, which involves only supercell force calculations. Pronounced anomalies are predicted for the [110] direction, which are similar to the ones observed for rhodium. First results of an inelastic neutron scattering investigation of the phonon dispersions are in very good agreement with the ab initio calculations and confirm the predicted anomalies. We present all interatomic force constants up to the 12th-nearest-neighbour shell obtained by a least-squares fit to supercell force constants of four different supercells. Theoretical phonon densities of states and elastic constants are compared with experimental data.