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  • Letter
  • Open Access

Many-body theory calculations of positron binding to halogenated hydrocarbons

J. P. Cassidy1,*, J. Hofierka1, B. Cunningham1, C. M. Rawlins1, C. H. Patterson2, and D. G. Green1,†

  • 1School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast BT7 1NN, United Kingdom
  • 2School of Physics, Trinity College Dublin, Dublin 2, D02 PN40, Ireland

  • *jcassidy18@qub.ac.uk
  • †d.green@qub.ac.uk
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Phys. Rev. A 109, L040801 – Published 22 April, 2024

DOI: https://doi.org/10.1103/PhysRevA.109.L040801

Abstract

Positron binding energies in halogenated hydrocarbons are calculated ab initio using many-body theory. For chlorinated molecules, including planars for which the interaction is highly anisotropic, very good to excellent agreement with experiment and recent density-functional-theory-based model-potential calculations is found. Predictions for fluorinated and brominated molecules are presented. The comparative effect of fluorination, chlorination, and bromination is elucidated by identifying trends within molecular families including dihaloethylenes and halomethanes based on global molecular properties (dipole moment, polarizability, ionization energy). It is shown that relative to brominated and chlorinated molecules, fluorinated molecules generate a less attractive positron-molecule potential due to larger ionization energies and smaller density of molecular orbitals close to the highest occupied molecular orbital, resulting in very weak, or in most cases loss of, positron binding. Overall, however, it is shown that the global molecular properties are not universal predictors of binding energies, exemplified by consideration of CH3Cl vs cis-C2H2F2: Despite the latter having a larger dipole moment, lower ionization energy, and similar polarizability, its binding energy is significantly smaller (25 vs 3 meV, respectively), owing to the important contribution of multiple molecular orbitals to, and the anisotropy of, the positron-molecule correlation potential.

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Phys. Rev. A 109, L040801– Published 22 April, 2024
  • Received 31 August 2023
  • Accepted 7 March 2024
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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