Speaker
Description
Recently, it was found that the positronic complex with (H−)2 can form the stable bound state concerning the dissociation into H− + PsH by a positron mediate bonding. This bonding situation, which resembles the well-defined single covalent bond, was qualified as “positronic covalent bonding”. On the other hand, a similar binding mechanism may be possible for anion dimers of other alkali species, such as lithium. In this study, we have investigated the stabilities of [X−; e+; X−] homonuclear systems with X = H and Li using the quantum Monte Carlo method combined with the multi-component molecular orbital calculation.
Our results show that the system has a single energy minimum in all the PECs, and its internuclear distance is drastically shortened by improving the accuracy of interparticle correlation effects. According to the characteristics of the electron and positron densities, the energy minimum structure at the HF level appears like a positronic covalent bonding, whereas the compact structure predicted at the DMC level may have strongly delocalized characters of both one excess electron and a positron.
By evaluating PECs of both lower energy decays into Ps + Li2− and Ps− + Li2, we confirmed that the [Li−; e+; Li−] system is stable for both these thresholds. The analytical results suggest that the dominant structure is depicted as Ps binding to Li2 anion, which is different from the [H−; e+; H−] case with a locally stable covalent positronic bonded structure.
