Electron diffraction study of short-range-order diffuse scattering from disordered binary alloys

A qualitative study was made by electron diffraction of the short-range-order diffuse scattering from disordered Au-Pd, α phase Au-Zn, and α phase Ag-Mg alloys. Twofold and fourfold splittings of diffuse maxima are observed at 100, 110 and equivalent positions on the diffraction patterns with the incident beam parallel to [001], in the composition ranges from about 28 to 62 at.% Pd for Au-Pd, from about 7 to 24 at.% Zn for Au-Zn and from about 11 to 28 at.% Mg for Ag-Mg systems. The separation of the split diffuse maxima increases monotonically with Pd, Zn or Mg content. The results can be interpreted with the Fermi-surface-imaging concept proposed by Krivoglaz. The variation with composition of the Fermi wave vector parallel to the [110] directions is discussed with the nearly-free-electron and the rigid-band models. The latter model is also applied to the experimental results for disordered Cu-Pd and Cu-Pt alloys reported by the present authors [Ohshima & Watanabe (1973). Acta Cryst. A29, 520-526].