Full correlation single-particle positron potentials for a positron and a positronium interacting with atoms

TL;DR

This paper develops and validates accurate single-particle potentials for positrons and positronium interacting with light atoms, capturing correlations and enabling transferability to condensed phases.

Contribution

It introduces a method to define exact single-particle potentials from many-body wavefunctions, including positronium formation, and compares them with density-functional theory results.

Findings

The potentials accurately reproduce scattering lengths and phase shifts.

Density-functional theory potentials agree well with many-body results.

The potentials are transferable to weakly interacting molecular and condensed systems.

Abstract

In this work we define single-particle potentials for a positron and a positronium atom interacting with light atoms (H, He, Li and Be) by inverting a single-particle Schr\"odinger equation. For this purpose, we use accurate energies and positron densities obtained from the many-body wavefunction of the corresponding positronic systems. The introduced potentials describe the exact correlations for the calculated systems including the formation of a positronium atom. We show that the scattering lengths and the low-energy s-wave phase shifts from accurate many-body calculations are well accounted for by the introduced potential. We also calculate self-consistent two-component density-functional theory positron potentials and densities for the bound positronic systems within the local density approximation. They are in a very good agreement with the many-body results, provided that the finite-positron-density electron-positron correlation potential is used, and they can also describe systems comprising a positronium atom. We argue that the introduced single-particle positron potentials defined for single molecules are transferable to the condensed phase when the inter-molecular interactions are weak. When this condition is fulfilled, the total positron potential can be constructed in a good approximation as the superposition of the molecular potentials.