Electron diffraction study of short-range-order diffuse scattering from disordered Cu–Pd and Cu–Pt alloys

The short-range-order diffuse scattering from disordered Cu-Pd and Cu-Pt alloys has been studied by electron diffraction using thin foils prepared from bulk specimens. Twofold and fourfold splittings of diffuse scattering are observed at 100, 110 and equivalent positions in the composition ranges from about 13 to 60 at.% Pd in the Cu-Pd system and up to about 45 at.% Pt in the Cu-Pt system. The separation of the split maxima increases with Pd or Pt content. A close investigation has revealed that the split maxima correspond to the intersections of slightly curved diffuse streaks around the 100 and 110 positions. These results can be interpreted well using the Fermi-surface-imaging theory proposed by Krivoglaz, indicating that the interaction potential in these alloys mainly originates from conduction electrons, and that the diffuse scattering reflects the form of the Fermi surface, i.e. the flatness normal to the (110) directions.