Calculation of spin-dependent momentum distributions in iron: Compton scattering and positron annihilation

Abstract

Spin-dependent momentum distributions in ferromagnetic iron are calculated in detail using the linear combination of Gaussian orbitals method. Theoretical results for Compton scattering and positron annihilation are presented in the form of momentum distributions, Compton profiles, one-dimensional angular correlation of annihilation radiation curves, Lock-Crisp-West folded plots and reciprocal form factors B(z), and are compared with experiment wherever possible. It is observed that the present theoretical results show satisfactory agreement with experiment. It is further observed that although the different theories (e.g. augmented plane waves, linear muffin-tin orbitals, present linear combination of Gaussian orbitals) agree among each other about the spin-dependent momentum distributions in ferromagnetic iron, minor differences exist between these theories and experiment. These differences are ascribed to the limitations of the independent-particle approximation, in particular to the effects of non-locality, e^--e^- and e⁺-e^- many-body correlations, etc.