Electron momentum-space densities and Fermi surface of Li100-xMgx (0 = x = 40) alloys: Compton scattering experiment versus theory

摘要

Directional Compton profiles (CP's) of Li100-xMgx (0 less than or equal to x less than or equal to 40) were measured for (11)12 directions of the momentum transfer q with (0.14) 0.16 a.u. (a.u. = atomic units: h = e = m = 1) momentum space resolution using synchrotron x rays, monochromatized to (31) 59 keV (values in brackets refer to x = 0). The total experimental valence electron CP's, their second derivatives, and the associated directional differences were compared with the corresponding Korringa-Kohn-Rostoker-coherent-potential-approximation-local-density-appr oximation (KKR-CPA-LDA) computations. Discrepancies between measurements and calculations are partly traced back to an inadequate treatment of electron correlation effects within the LDA framework. The three-dimensional (3D) valence-electron momentum density, rho(p), as well as the 3D occupation number density N(k), were reconstructed from experimental data using the Fourier-Bessel method. The reconstructed rho(p)'s exhibit evidence of higher momentum components due to 110 umklapp processes, whose variations with x are in reasonable agreement with the KKR-CPA calculations. The experimental N(k)'s provide a direct measure of the Fermi-surface anisotropy and show the presence of necks on the 110 Brillouin-zone boundaries for x greater than or equal to 13 in good accord with 2D positron annihilation experiments. [S0163-1829(99)14833-1]. [References: 53]