Positron correlation energy in metals

The positron correlation energy in an electron gas is calculated in the metallic density region using the random phase dielectric constant. It is found that the positron–plasmon interaction is much more important for the correlation energy than for the annihilation rate, and that the plasmon contribution to the energy is actually larger than the particle–hole contribution. Calculations using the Singwi et al. dielectric constant give essentially the same results as the RPA. It is argued that the ladder approximation need not represent an improvement over linear response theory when computing the correlation energy.