Correlated Wave Functions for Electron-Positron Interactions in Atoms and Molecules

The positron, as the antiparticle of the electron, can form metastable stateswith atoms and molecules before its annihilation with an electron. Such metastablematter-positron complexes are stabilized by a variety of mechanisms, which can have bothcovalent and noncovalent character. Specifically, electron-positron binding often involvesstrong many-body correlation effects, posing a substantial challenge for quantum-chemicalmethods based on atomic orbitals. Here we propose an accurate, efficient, and transferablevariational ansatz based on a combination of electron-positron geminal orbitals and aJastrow factor that explicitly includes the electron-positron correlations in thefield of thenuclei, which are optimized at the level of variational Monte Carlo (VMC). We apply thisapproach in combination with diffusion Monte Carlo (DMC) to calculate binding energiesfor a positrone+and a positronium Ps (the pseudoatomic electron-positron pair), bound to a set of atomic systems (H-,Li+, Li,Li-,Be+, Be, B-,C-,O-and F-). For PsB, PsC, PsO, and PsF, our VMC and DMC total energies are lower than that from previouscalculations; hence, we redefine the state of the art for these systems. To assess our approach for molecules, we study the potential-energy surfaces (PES) of two hydrogen anions H-mediated by a positron (e+H22-), for which we calculate accurate spectroscopicproperties by using a dense interpolation of the PES. We demonstrate the reliability and transferability of our correlated wavefunctions for electron-positron interactions with respect to state-of-the-art calculations reported in the literature.

Automated summary

The article introduces an accurate, efficient, and transferable variational ansatz based on a combination of electron-positron geminal orbitals and a Jastrow factor. This ansatz explicitly includes the electron-positron correlations and is optimized using variational Monte Carlo. The approach is applied to calculate binding energies for various atomic and molecular systems, showing improved accuracy compared to previous calculations.