Unveiling the potential of superalkali cation Li3+ for capturing nitrogen

The potential of the superalkali cation Li-3(+) for capturing N-2 and its behavior in gaseous nitrogen have been theoretically studied at the MP2/6-311+G(d) level. The evolution of structures and stability of the Li-3(+)(N-2)(n) (n = 1-7) complexes shows that the N-2 molecules tend to bind to different vertices of the Li-3(+) core, and that Li-3(+) might have the capacity to capture up to twelve nitrogen molecules in the first coordination shell. Based on natural population and molecular orbital analyses, Li-3(+) keeps its superatom identity in the lowest-lying Li-3(+)(N-2)(n) (n = 1-4) complexes. The change in the Gibbs free energies of possible fragmentation channels also indicates the thermodynamic stability of Li-3(+) in the (N-2)(n) clusters when n <= 4. Different from the case of Li-3(+)(H2O)(n), where the electrostatic interaction is dominant, the electrostatic and polarization components are found to make nearly equal contributions to Li-3(+)(N-2)(n) complex formation. In addition, it can be concluded that the superalkali cation Li-3(+) surpasses heavy alkali metal cations in capturing N-2 molecules, since it has a larger binding energy with N-2 than Na+ and K+ ions.