  We make a gradient correction to a new local density approximation form of
positron-electron correlation. Then the positron lifetimes and affinities are
probed by using these two approximation forms based on three
electronic-structure calculation methods including the full-potential
linearized augmented plane wave (FLAPW) plus local orbitals approach, the
atomic superposition (ATSUP) approach and the projector augmented wave (PAW)
approach. The differences between calculated lifetimes using the FLAPW and
ATSUP methods are clearly interpreted in the view of positron and electron
transfers. We further find that a well implemented PAW method can give
near-perfect agreement on both the positron lifetimes and affinities with the
FLAPW method, and the competitiveness of the ATSUP method against the FLAPW/PAW
method is reduced within the best calculations. By comparing with experimental
data, the new introduced gradient corrected correlation form is proved
competitive for positron lifetime and affinity calculations.
