The nature of the newly proposed two-positron bond in (PsH)2, which is
composed of two protons, four electrons and two positrons, is considered in
this contribution. The study is done at the multi-component-Hartree-Fock
(MC-HF) and the Diffusion Monte Carlo (DMC) levels of theory by comparing ab
initio data, analyzing the spatial structure of the DMC wavefunction, and
applying the multi-component quantum theory of atoms in molecules and the
two-component interacting quantum atoms energy partitioning schemes to the
MC-HF wavefunction. The analysis demonstrates that (PsH)2 to a good
approximation may be conceived of two slightly perturbed PsH atoms, bonded
through a two-positron bond. In contrast to the usual two-electron bonds, the
positron exchange phenomenon is marginal in the considered two-positron bond.
The main stabilizing mechanism of bonding is a novel type of classical
electrostatic interaction between the positrons, which are mainly localized
between nuclei, and the surrounding electrons. To emphasize its uniqueness,
this mechanism of bonding is proposed to be called gluonic which has also been
previously identified as the main deriving mechanism behind formation of the
one-positron bond in [H-, e+, H-] . We conclude that the studied two-positron
bond should not be classified as a covalent bond and it must be seen as a
brand-new type of bond, foreign to the electronic bonding modes discovered so
far in the purely electronic systems.Comment: main text plus supporting informatio