The Influence of a positron on electron-positron momentum densities in metallic materials

General properties of the electron–positron (e–p) momentum densities were investigated in the extended momentum space (Kontrym-Sznajd et al 2012 Phys. Rev. B 85 245104). In this paper, a small selection of numerical tests of our theory is presented for the independent particle model in the simple and the transition metals. It is confirmed that the intensity of the Umklapp components of the electron densities is generally reduced by a positron. Nevertheless, some of them may be enlarged, provided the fulfilment of certain conditions which are discussed in detail. On the example of yttrium it is also demonstrated how the positron influences the electron momentum densities in the reduced zone. Our considerations are given for both the independent particle model and after including the e–p correlations within the local density approach.