Binding Matter with Antimatter: The Covalent Positron Bond.

We report sufficient theoretical evidence of the energy stability of the e+ ⋅H22- molecule, formed by two H- anions and one positron. Analysis of the electronic and positronic densities of the latter compound undoubtedly points out the formation of a positronic covalent bond between the otherwise repelling hydride anions. The lower limit for the bonding energy of the e+ ⋅H22- molecule is 74 kJ mol-1 (0.77 eV), accounting for the zero-point vibrational correction. The formation of a non electronic covalent bond is fundamentally distinct from positron attachment to stable molecules, as the latter process is characterized by a positron affinity, analogous to the electron affinity.