Chemical bonding in the lightest tri-atomic clusters; H3+, Li3+ and B3−

Detailed topological charge density analysis and the Quantum Theory of Atoms in Molecules (QTAIM) calculations has been performed on equilibrium geometries of the three lightest tri-atomic clusters; H3+, Li3+ and B3−. Characteristics of critical points of charge density, the effects of occupied molecular orbitals on topology of charge density, the stability of molecular graphs toward nuclear excursions and the QTAIM integration results were used to draw a picture of bonding in these clusters. Topological networks in H3+ and B3− are unstable but molecular graph of Li3+ is stable under finite geometry changes. H3+ is best represented as a 3-membered ring; lithium atoms in Li3+ surround the electrons in basin of a Non-Nuclear Maximum (NNM) by an electrostatic interaction; and in B3− an extended bonding pattern was found.