Various cyclic N_8 isomers are considered at the levels of B3 LYP/6-311++G(d,p) and B3 LYP/c PVTZ. Some energies and molecular orbital properties are obtained. The structures are found to be stable in the singlet stat...Various cyclic N_8 isomers are considered at the levels of B3 LYP/6-311++G(d,p) and B3 LYP/c PVTZ. Some energies and molecular orbital properties are obtained. The structures are found to be stable in the singlet state but mostly unstable in the triplet. The heats of formation values calculated by means of T1 recipe reveals that they are highly endothermic. NICS(0) values have been calculated and aromaticity/antiaromaticity of the rings are discussed. Additionally, theoretical IR,UV-VIS spectra and the calculated impulse values have been obtained.展开更多
Polynitrogen compounds, comprising only nitrogen atoms, are rare. They are considered as promising candidates of clean(green) high energy density materials because of their high energy content and their sole decomposi...Polynitrogen compounds, comprising only nitrogen atoms, are rare. They are considered as promising candidates of clean(green) high energy density materials because of their high energy content and their sole decomposition product is N_2. Extending the previous work which was on cyclic N_8 isomers, in this study some cyclic N_(10) isomers having 1-4 cycles are considered within the limitations of density functional theory at the levels of B3LYP/6-311++G(d,p) and B3LYP/cc-PVTZ. Some of the structures,including the monocyclic one, decompose by eliminating certain number of N_2 units while some remain intact. All the stable isomers(1-3, 6-8) investigated presently are highly endothermic that they are candidates for clean high energy materials. Certain quantum chemical properties, IR and UV-VIS spectra as well as the specific impulse values for the stable structures are reported.展开更多
Developing metal-free, carbon-based catalysts to replace platinum-based catalysts for oxygen reduction reactions （ORRs） is an emerging area of research. In recent years, different carbon structures including carbon ...Developing metal-free, carbon-based catalysts to replace platinum-based catalysts for oxygen reduction reactions （ORRs） is an emerging area of research. In recent years, different carbon structures including carbon doped with IIIA-VIIA heteroatoms （C-M site-based, where M represents the doped heteroatom） and polynitrogen （PN） compounds encapsulated in carbon nanotubes （CNTs） （N N site-based） have been synthesized. Compared to metallic catalysts, these materials are highly active, stable, inexpensive, and environmentally friendly. This review discusses the development of these materials, their ORR performances and the mechanisms for how the incorpora- tion of heteroatoms enhances the ORR activity. Strategies for tailoring the structures of the carbon substrates to improve ORR performance are also discussed. Future studies in this area will need to include optimizing synthetic strategies to control the type, amount and distribution of the incorporated heteroatoms, as well as better understanding the ORR mechanisms in these catalysts.展开更多
文摘Various cyclic N_8 isomers are considered at the levels of B3 LYP/6-311++G(d,p) and B3 LYP/c PVTZ. Some energies and molecular orbital properties are obtained. The structures are found to be stable in the singlet state but mostly unstable in the triplet. The heats of formation values calculated by means of T1 recipe reveals that they are highly endothermic. NICS(0) values have been calculated and aromaticity/antiaromaticity of the rings are discussed. Additionally, theoretical IR,UV-VIS spectra and the calculated impulse values have been obtained.
文摘Polynitrogen compounds, comprising only nitrogen atoms, are rare. They are considered as promising candidates of clean(green) high energy density materials because of their high energy content and their sole decomposition product is N_2. Extending the previous work which was on cyclic N_8 isomers, in this study some cyclic N_(10) isomers having 1-4 cycles are considered within the limitations of density functional theory at the levels of B3LYP/6-311++G(d,p) and B3LYP/cc-PVTZ. Some of the structures,including the monocyclic one, decompose by eliminating certain number of N_2 units while some remain intact. All the stable isomers(1-3, 6-8) investigated presently are highly endothermic that they are candidates for clean high energy materials. Certain quantum chemical properties, IR and UV-VIS spectra as well as the specific impulse values for the stable structures are reported.
文摘Developing metal-free, carbon-based catalysts to replace platinum-based catalysts for oxygen reduction reactions （ORRs） is an emerging area of research. In recent years, different carbon structures including carbon doped with IIIA-VIIA heteroatoms （C-M site-based, where M represents the doped heteroatom） and polynitrogen （PN） compounds encapsulated in carbon nanotubes （CNTs） （N N site-based） have been synthesized. Compared to metallic catalysts, these materials are highly active, stable, inexpensive, and environmentally friendly. This review discusses the development of these materials, their ORR performances and the mechanisms for how the incorpora- tion of heteroatoms enhances the ORR activity. Strategies for tailoring the structures of the carbon substrates to improve ORR performance are also discussed. Future studies in this area will need to include optimizing synthetic strategies to control the type, amount and distribution of the incorporated heteroatoms, as well as better understanding the ORR mechanisms in these catalysts.
