Lattice dynamics and phonon line shapes ofPd0.9Ag0.1D0.61at 100 K

The phonon-dispersion relations in a ${\mathrm{Pd}}_{0.9}$ ${\mathrm{Ag}}_{0.1}$ ${\mathrm{D}}_{0.61}$ crystal have been determined by coherent neutron scattering techniques. In comparison to ${\mathrm{PdD}}_{\mathrm{x}}$ systems, a softening of the acoustic modes by 2% and a hardening of the optic modes by ≊4% is observed. Moreover, the optic-phonon groups are considerably broadened because of force-constant disorder when compared to ${\mathrm{PdD}}_{\mathrm{x}}$. Finally, the present results are discussed in view of the high superconducting transition temperature occurring in the ${\mathrm{Pd}}_{1\mathrm{-}\mathrm{y}}$ ${\mathrm{Ag}}_{\mathrm{y}}$ ${\mathrm{D}}_{\mathrm{x}}$ system.