Ground-state energy of quasi-free positrons in non-polar fluids

We have calculated the background energy ($V_0$) for positrons in noble gases with an \emph{ab initio} potential and Wigner-Seitz (WS) ansatz. {\col In contrast to general pseudo-potential approach, we used accurate potentials positron-atom interaction.} The ansatz includes assumed form of potential, resulting from average over fluid atoms, propose four different options this. By comparing literature data effective electron number ($Z_{\text{eff}}$), find that agreement can be obtained light elements, but fails heavy elements. suspect strong polarizability elements makes simple averaging, as model, insufficient fit measurements without also making use pseudo-potentials. raise our suspicion comparison annihiliation rates between ground-state calculations experimental values is not appropriate. Furthermore, congruence $V_0$ $Z_{\text{eff}}$ predicted by a contact approximation appears invalidated results.