Lattice Dynamics of Cu1-x - Nix

The phonon dispersion relations for the (110) direction in the alloy Cu0,9 -Ni0,1 and pure copper have been measured by the method of inelastic scattering of slow neutrons using the time-of-flight spectrometer at the 10-MW research reactor JRR-2 in Tokai. The measurements were made at room temperature. There are significant differences in the shapes of the dispersion curves for Cu0,9 -Ni0,1, as compared with the results for Cu. Those of Cu0,9 -Ni0,1 show large anomalies in the range of reduced wave number q = 0.5 to 1.1 for both 1 and T2 branches. This is in contrast to the very smooth behaviour on the dispersion curves for copper and also for nickel. The range of the forces of interactions was determined by performing least-squares fits of the experimental dispersion relations for Cu and C0,9 -Ni0,1 to Fourier series of the form 4π2Mv2 = Σ/n An(1- cos nπq/qm), where An represent the interplanar force constants for the nth neighbour's plane. For C0,9 -Ni0,1 seven planes at least are needed to fit the observed dispersion curves in both branches, as compared with three planes needed to obtain a reasonable fit for Cu. This fact indicates that the force constants between distant neighbours for alloys are larger than those for Cu. (author)