Lattice Instability in β1-AgZn

Phase transition of β 1 -AgZn alloy was studied by means of neutron inelastic and diffuse scattering techniques. Acoustic phonon dispersion relation along the main crystal axes of the alloy was obtained. No [ζζζ]LA phonon anomalies related to the ζ-phase was observed, although previous sound experiment followed by elastic constant analysis predicts that possibility. The observed anomalies in phonon energy of both [ζζ0]TA 1 and [ζζ-2ζ]TA modes associated with the diffuse scattering peaks indicate that a strong lattice instability is involved in the phonon modes. It is pointed out that the lattice instability plays important roles in the structure transition from β 1 -phase to ζ-phase or to the martensitic phase in the AgZn alloy.