Theoretical Studies On Energetic Materials:All-nitrogen Molecules Encapsulated Inside Nanoscale Boron Nitrogen Cages And Tube

All-nitrogen compounds as promising candidates for high-energy density materials?HEDMs?will play important roles in the fields of defense and economy construction.Here,we calculated the polynitrogen compounds with encapsulated all-nitrogen?N_n?molecules by three density functional methods:B3LYP,?B97X-D and B3LYP-D3.The main results are described as follows:?1?A serials of polynitrogen compounds composed by encapsulated N_n clusters and two types of B₂₄N₂₄ fullerene-like nanocages are systematically investigated.The calculated results indicate that the O symmetric B₂₄N₂₄(o-B₂₄N₂₄)nanocage could encapsulates a maximum of 10 nitrogen atoms,and the S₈ symmetric B₂₄N₂₄(s-B₂₄N₂₄)nanocage could encapsulates a maximum of 9.The encapsulated N_n in N_n@o-B₂₄N₂₄ have the similar configurations for n=1-5,7,and the different configurations of n=6,8,9 to those in N_n@s-B₂₄N₂₄.The results of total energies,percentage relative elongation of B₂₄N₂₄ and energies per nitrogen atom of the encaged N_n all indicate that the s-B₂₄N₂₄ nanocage is better for n?5,and worse for n?6 than the o-B₂₄N₂₄ nanocage for encapsulating the N_n clusters.In addition,the HOMO-LUMO energy gaps of N_n@B₂₄N₂₄ generally show a gradual decrease with the increase of the number of nitrogen atom of the encaged N_n in odd or even number.?2?A serials of polyitrogen compounds consisting of encapsulated N_n clusters and boron nitride nanotube?BNNT?are systematically investigated by density functional theory.All of the binding energies for N_n@BNNT?n=1-10?complexes are negative,suggesting that the encaged N_n clusters could exist in the BNNT.In addition,the more negative binding energies of N₅@BNNT?N₇@BNNT-1 than others indicat that the N_n clusters consisting of alone N₅ ring could be more likely to be found or synthesized in BNNT.The atoms in molecules?AIM?and the non-covalent interaction?NCI?analyses show that the interactions between N_n clusters and BNNT mainly are van der Waals interactions.The natura bond orbital?NBO?analysis shows that the obvious charge transfers between encapsulated N_n clustes and BNNT only appear in N₅@BNNT?N₇@BNNT-1,which indicates the alone N₅ ring could improve the stabilities of the encapsulated complexes.The frontier molecular orbital analyses for N_n@BNNT?n=1-10?complexes indicate that the encapsulated N_n clusters mainly influence the LUMO of BNNT,so that the HOMO-LUMO gap changes.