Electron-positron momentum densities in crystalline solids

The uniqueness of information contained in electron densities ρ(p) in the extended momentum space is pointed out, showing that certain electronic properties can be derived only from ρ(p), directly related to the electron Bloch wave functions. The influence of many-body effects on the electron–positron (e–p) momentum density and of the crystal lattice periodicity on scattering effects is discussed. On the example of Mg it is illustrated that for simple metals there is a unique opportunity to estimate, for e–p densities, electron–electron correlation effects quantitatively.