Erlangen 2022 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 6: Theory

MO 6.4: Vortrag

Dienstag, 15. März 2022, 11:15–11:30, MO-H7

Explicitly correlated wave functions for electron-positron interactions in atoms and molecules — •Jorge Charry, Matteo Barborini, and Alexandre Tkatchenko — University of Luxembourg, Luxembourg, Luxembourg

Positrons are capable of forming metastable states with atoms and molecules before the electron-positron annihilation process[1]. Such metastable matter–positron complexes are stabilized by a variety of mechanisms, which can have both covalent and non-covalent character. The study of these systems represents a challenge for quantum-chemical methods due to the need to describe the strong attractive correlation effects, which are limited by the employment of atom-centered basis sets to describe the positronic orbitals. In this work, we present a robust variational ansatz based on a combination of an electronic determinant, electron–positron pairing orbitals, and a Jastrow factor to explicitly accounts for the electron-positron correlations in the nuclear field, which are optimized at the level of variational Monte Carlo (VMC). We apply this approach in combination with diffusion Monte Carlo (DMC) to calculate binding energies for a positron e⁺ bound to a set of neutral and anionic first-row atoms. To assess our approach for molecules, we study the interaction potential of the previously reported [2] system of two hydrogen anions H⁻ mediated by a positron (H⁻·e⁺ · H⁻). We demonstrate the reliability and transferability of our correlated wavefunctions with respect to state-of-the-art calculations reported in the literature. [1] G. F. Gribakin, et al., Rev. Mod. Phys 82, 2557 (2010). [2] J. Charry, et al., Angew. Chemie 57, 8859 (2018)