The Fermi surface of Hume-Rothery phases in Ag-Al and Cu-Ge alloys studied by a positron annihilation method

Abstract Hexagonal-close-packed single crystals of Ag-Al and Cu-Ge alloys have been investigated by angular correlations of annihilation photon pairs. The three-dimensional momentum density distribution was reconstructed by means of Mijnarends’ method from the experimental data along five orientations. Over the range of electron concentration e/a = 1.4–1.8, the anisotropic features of the Fermi surface were determined in the ГML and ГMK sections; e.g. at e/a = 1.57 there exist a neck near the symmetry point г, a bulge towards L, an overlapping electron-sheet near M and a hole state near K.

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