Calculation of momentum distributions in paramagnetic chromium: compton scattering and positron annihilation

Abstract

A detailed calculation of the momentum distributions in paramagnetic (BCC) chromium is carried out using the linear combination of Gaussian orbitals (LCGO) method. Using the same electron wavefunctions, theoretical results are obtained for Compton scattering and positron annihilation, and are presented in the form of electron momentum distributions rho (p), reciprocal form factors B(z), two-photon momentum distributions rho ^{2 gamma} (p), one-dimensional angular correlation of positron annihilation radiation, Lock-Crisp-West distributions, etc. These results are analysed in terms of the Fermi surface topology of paramagnetic Cr. In particular, the present results for rho ^{2 gamma} (p) are compared with those reconstructed by Kubota et al (1991) from their two-dimensional angular correlation of positron annihilation radiation measurements. Observed differences are ascribed to the effects of e⁺-e^- many-body correlations and the reconstruction procedure.