Electronic and Positronic Structure of Diamond under Normal and High Pressure

Empirical nonlocal pseudopotentials of diamond which can describe the electronic energy structure over a wide energy range of more than 20 eV from the bottom of the valence band are determined. The nonlocality of the potential is described by the Gaussian model. The optimized nonlocal pseudopotential reproduces the energy band structure within 5%. The valence electron and positron charge densities in diamond are obtained from wave functions derived from this model at normal and under hydrostatic pressure. It is found that the positron density is maximum in the open interstices and is excluded not only as usual, from the ion cores but also to a considerable degree from the valence bonds.