Lattice Dynamics of the Force Constant Disordered Crystal Pd 0.90 Ru 0.10

Phonon dispersion relations for Pd 0.90 Ru 0.10 single crystal at room temperature are measured along the directions [100], [110], and [111] by inelastic neutron scattering. The Born‐von Karman analysis, using the seven‐neighbour model, is carried out, and the force constants and elastic constants are calculated. The phonon frequency shifts, Δω( q ), and the self‐energy functions, ∑ j ( q , ω j ( q )), for all the branches are determined from the experimental phonon data for Pd 0.90 Ru 0.10 and Pd. The self‐energy shows a rich and coherent structure and reveals unique information relevant to a theoretical model of a phonon induced fast diffusion in certain metals. The same structure of the self‐energy is observed in the sample after annealing at 1420°C.