Chain or Ring: Which One Is Favorable in Nitrogen-Rich Molecules N₆XH<i>_m</i>, N₈XH<i>_m</i>, and N₁₀XH<i>_m</i> (X = B, Al, Ga, <i>m</i> = 1 and X = C, Si, Ge, <i>m</i> = 2)?

Abstract

A series of nitrogen-rich molecules N₆XH_<i>m</i>, N₈XH_<i>m</i>, and N₁₀XH_<i>m</i> (X = B, Al, Ga, <i>m</i> = 1 and X = C, Si, Ge, <i>m</i> = 2) consisting of N₃ and N₅ radicals, are systematically investigated by using B3LYP and B3PW91 DFT methods. It is found that for the nitrogen-rich molecules, the structures with N₃-chains (N₅-ring) are more stable than those containing a N₃-ring (N₅-chain). This result could be well-explained by the intrinsic stability of the N₃ and N₅ radicals and their charge distribution in nitrogen-rich molecules. The dissociation energies further indicate that the B-doped and C-doped structures are the most stable among the molecules with three elements of group 13 and 14, respectively. Energy decomposition analysis shows the bond of boron–nitrogen is stronger than that of carbon–nitrogen. Detailed bonding analysis demonstrates that the B–N bond is determined by σ and π interactions between the B and N atoms, whereas C–N bonds by only σ interactions. These results imply that the boron atom is more suitable than the carbon atom for building the nitrogen-rich molecules studied in this article