In this letter, we propose a functional on the basis
of the Schwinger
variational principle that accounts for the particle rearrangement
by solving a projected Lippmann–Schwinger equation system.
The method is tested in the static-coupled approximation for positron-H,
where excellent agreements with benchmark results are found for the
elastic, positronium (Ps) formation and annihilation cross sections.
The effect of virtual Ps formation is evidenced through the analysis
of the annihilation map. A significant increase in the electron–positron
density in the vicinity of the atom is obtained.