Many-body theory calculations of positronic-bonded molecular dianions

Abstract

The energetic stability of positron di-anion systems [A${}^{-};e^{+};$A${}^{-}$] is studied via many-body theory, where $A^{-}$ includes H${}^{-}$, F${}^{-}$, Cl${}^{-}$ and the molecular anions (CN)${}^{-}$ and (NCO)${}^{-}$. Specifically, the energy of the system as a function of ionic separation is determined by solving the Dyson equation for the positron in the field of the two anions, using a positron-anion self energy as constructed in [J. Hofierka, B. Cunningham, C. M. Rawlins, C. H. Patterson and D. G. Green, \emph{Nature} {\bf 606} 688 (2022)] that accounts for correlations including polarization, screening, and virtual-positronium formation. Calculations are performed for a positron interacting with H${}_2^{2-}$, F${}_2^{2-}$, and Cl${}_2^{2-}$, and are found to be in good agreement with previous theory. In particular, we confirm the presence of two minima in the potential energy of the [H${}^{-};e^{+}$;H${}^{-}$] system with respect to ionic separation: one a positronically-bonded [H${}^{-};e^{+}$;H${}^{-}$] local minimum at ionic separations $r\sim 3.4$~Å\phantom{}, and a global minimum at smaller ionic separations $r\lesssim 1.6$~Å\phantom{} that gives overall instability of the system with respect to dissociation into a H${}_2$ molecule and a positronium negative ion, Ps${}^{-}$. The first predictions are made for positronic bonding in dianions consisting of molecular anionic fragments, specifically for (CN)${}_2^{2-}$, and (NCO)${}_2^{2-}$. In all cases we find that the molecules formed by the creation of a positronic bond are stable relative to dissociation into A${}^{-}$ and $e^{+}$A${}^{-}$ (positron bound to a single anion), with bond energies on the order of 1~eV and bond lengths on the order of several \r angstroms.

References in corpus (8)

• Many-body theory of positron-atom interactions
• Positron scattering and annihilation on noble gas atoms
• Many-body theory of positron binding in polyatomic molecules
• Many-Body Theory Calculations of Positron Scattering and Annihilation in H${}_2$, N${}_2$ and CH${}_4$
• On the nature of the positronic bond
• Many-body Theory Calculations of Positron Binding to Halogenated Hydrocarbons
• The three-center two-positron bond
• Gaussian-basis many-body theory calculations of positron binding to negative ions and atoms

Cited by in corpus (5)

• Many-body Theory Calculations of Positron Binding to Halogenated Hydrocarbons
• Positron annihilation and binding in aromatic and other ring molecules
• Many-body theory predictions of positron binding energies in five-membered heterocycles involving N, O, S and NH substituents
• Coupled cluster theory for positron binding in anions and polyatomic molecules
• The two-positron gluic bond as a manifestation of "super" van der Waals interactions