Low ionization potentials of Na4OCN superalkali molecules

The structure and properties of hypermetalated Na4OCN molecules and their corresponding Na4OCN+ daughter cations were investigated using ab initio methods at the CCSD(T)/6-311+G(3df)//MP2/6-311+G(d) level of theory. Eight neutral Na4OCN geometrically stable isomers were found to possess similar electronic energies. The vertical ionization potentials (IP) of the Na4OCN isomeric systems (determined at the OVGF/6-311+G(3df) level) were calculated to span the 4.117-4.640 eV range, which allows the classification of the Na4OCN species as superalkali molecules (the predicted ionization potentials are smaller than the IP of the Na atom, 5.14 eV). The global minimum on the Na4OCN ground-state neutral potential energy surface was found to correspond to the kite-shaped structure whose vertical IP was estimated to be 4.478 eV.