Electron momentum distribution in Al and Al0.97Li0.03

High resolution Compton profiles from single crystals of Al and Al0.97Li0.0 3 have been measured along the principal crystallographic directions [100], [110], and [111] using monochromatic synchrotron radiation at two differen t photon energies. The spectra were recorded by a scanning spectrometer wit h a momentum resolution of 0.08 a.u. for 29 keV and 0.16 a.u. for 58 keV ra diation. Corresponding, highly accurate computations on Al0.97L0.03 and Al have been carried out within the framework of the selfconsistent KKR-CPA sc heme, including the limiting case of a single impurity. A good overall acco rd is found between theory and experiment with respect to the anisotropies as well as the amplitudes and fine structure in the first and second deriva tives of the directional profiles. The Fermi break is found to be the sharp est along the [111] direction in Al and the alloy. The [110] direction show s an anomalously large discrepancy between theory and experiment near the F ermi momentum, suggesting that the present LDA based crystal potential does not reproduce fine details of the electron rings of the 3rd band in Al acc urately. The effects of alloying are analyzed by taking differences between profiles of Al and Al0.97Li0.03. and it is shown that these results can be explained to a first approximation within a free electron model by the dep letion of 0.06 electrons/atom from the Fermi surface of Al. (C) 2001 Elsevi er Science Ltd. All rights reserved.