Many-body theory calculations of positronic-bonded molecular dianions
- URL: http://arxiv.org/abs/2311.16318v1
- Date: Thu, 23 Nov 2023 12:09:37 GMT
- Title: Many-body theory calculations of positronic-bonded molecular dianions
- Authors: J. P. Cassidy, J. Hofierka, B. Cunningham and D. G. Green
- Abstract summary: We study the energetic stability of positron di-anion systems [A$-;e+;$A$-$] via many-body theory.
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.
First predictions are made for positronic bonding in dianions consisting of molecular anionic fragments, specifically for (CN)$_22-$, and (NCO)$_22-$.
- Score: 0.0
- License: http://creativecommons.org/licenses/by/4.0/
- 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 $r\sim3.4$~\AA\phantom{}, and a global
minimum at smaller ionic separations $r\lesssim1.6$~\AA\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.
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