Electron-positron interaction in light elements represented by atoms embedded in an electron gas

Mijnarends et al. [J. Phys. Condens. Matter {\bf 10}, 10383 (1998)] contested the best existing calculations of positron annihilation rates in jellium and crystal lattices, pointing in this way at deficiencies of existing theories of electron-positron interaction in these materials. In the present work the local enhancement factors due to positron-electron interaction in Li, Be, B, C, N and O are computed in a consequent many-body approach for core and as concerns lithium also for conduction electrons and compared to the results of existing approximations to this problem which avoid direct many-body calculations in metals, i.e. the local density, generalized gradient and weighted density approximations, as well as to experimental data. Conclusions about positron lifetime and positron-electron correlation energy are also presented. Suggestions concerning annihilation rates in an electron gas agree with those of Mijnarends et al.