Structural Properties of High-Energy NC Molecules: Cyclic Hexamers of NCN.

Molecules with high nitrogen content are of interest for their potential as high-energy materials. However, many molecules with 100% nitrogen content are unstable and dissociate with low barriers, which limits practical applications. In the present study, cyclic hexamers of the basic unit NCN (70% nitrogen by mass) are studied to determine the structural features and bonding characteristics that lead to more stable molecules.

N22C2 versus N24: role of molecular curvature in determining isomer stability.

Three-dimensional N(22)C(2) cages are examined by theoretical calculations to determine relative stability among various isomers. Stability as a function of cage shape and stability as a function of carbon location are calculated and discussed. The results are compared to isomers of N(24) to determine the effects of carbon substitution into the cage structure.

Structure and decomposition energies of high-energy open-chain carbon-nitrogen compounds N(x)C(2).

Molecules and ions consisting entirely or predominantly of nitrogen are of interest because of their energy release properties. Such molecules can decompose into N(2), a process that is very exothermic. Following a study predicting the stability properties of isomers of open-chain N(4)C(2), the current study involves calculations on a series of open-chain carbon-nitrogen molecules.

Metal-ion binding to high-energy N12C4.

Carbon-nitrogen compounds are of interest for their potential as high-energy materials. One major issue in determining the structures of high-energy materials is molecular stability; a more stable energetic compound is more likely to be useful in a wider variety of applications. In this study, binding energies are calculated for a high-energy N(12)C(4) structure with a series of metal ions to determine preferred binding sites.

Stability and Dissociation Energies of Open-Chain N4C2.

Complex forms of nitrogen are of interest due to their potential as high-energy materials. Many forms of nitrogen, including open-chain and cage molecules, have been studied previously. While many all-nitrogen molecules Nx have been shown to be too unstable for high-energy applications, it has been shown that certain heteroatoms (including carbon) can stabilize a nitrogen structure.

Stability of N18C6H6: triangular versus hexagonal structure.

Large nitrogen cage molecules Nx have been previously shown to prefer elongated, cylindrical structures with triangular caps versus more spherical structures composed entirely of pentagons and hexagons. It was argued that this preference derived from the electronic properties of the nitrogen atoms, including the lone pairs. In the current study, the same structural comparison is carried out, with the substitution of C-H-bonding groups for six of the nitrogens.

Stability of N10C10H10 and N12C12H12 Cages and the Effects of Endohedral Atoms and Ions.

Cages of carbon and nitrogen have been studied by theoretical calculations to determine the potential of these molecules as high-energy density materials. Following previous theoretical studies of high-energy N6C6H6 and N8C8H8 cages, a series of calculations on several isomers of the larger N10C10H10 and N12C12H12 is carried out to determine relative stability among a variety of three-coordinate cage isomers with four-membered, five-membered, and/or six-membered rings. Additionally, calculations are carried out on the same molecules with atoms or ions inside the cage.

Isomer stability and bond-breaking energies of N8C8H8 cages.

Molecules consisting entirely or predominantly of nitrogen have been extensively investigated for their potential as high-energy density materials (HEDM). Such molecules react to produce N2 and large amounts of energy, but many such molecules are too unstable for practical applications. In the present study, cage isomers of N8C8H8 are studied using theoretical calculations to determine the structural features that lead to the most stable cages and determine the energetics of dissociation for the various isomers.

Stability of high-energy N14H4(2+) ion and the effects of carbon and halogen substitution.

Previous studies of oxygen addition into an N12 cage framework revealed the possibility of stable high-energy density materials (HEDM) resulting from such additions. In the current study, nitrogen addition into N12 is studied as a means of generating stable HEDM. Nitrogen addition into N12 is shown to yield an N14H4(2+) ion, which is examined by theoretical calculations to determine its stability with respect to dissociation.

Stability of nitrogen-oxygen cages N12O2, N14O2, N14O3, and N16O4.

Molecules consisting entirely of nitrogen have been studied extensively for their potential as high energy density materials (HEDM). However, many such molecules are too unstable to serve as practical energy sources. This has prompted many studies of molecules that are mostly nitrogen but which incorporate heteroatoms into the structure to provide additional stability.

Why isn't the N20 dodecahedron ideal for three-coordinate nitrogen?

Nitrogen molecules are the focus of much attention for their potential as high-energy density materials. The usefulness of such molecules as energy sources depends on the stability of the molecules with respect to dissociation. Many such molecules dissociate too easily to be a stable fuel, and the reasons for such instability are related to the details of structure and bonding of the molecule.

Isomer stability of N6C6H6 cages.

Recent theoretical studies have identified carbon-nitrogen cages that are potentially stable high energy density materials (HEDM). One such molecule is an N(6)C(6)H(6) cage in which a six-membered ring of nitrogen is bonded to C(3)H(3) triangles on both sides. This molecule is based on the structure of the most stable N(12) cage, with six carbon atoms substituted into the structure.

Boron nitride cages from B12N12 to B36N36: square-hexagon alternants vs boron nitride tubes.

The structures and stabilities of square-hexagon alternant boron nitrides (Bx Nx , x=12-36) vs their tube isomers containing octagons, decagons and dodecagons have been computed at the B3LYP density functional level of theory with the correlation-consistent cc-pVDZ basis set of Dunning. It is found that octagonal B20N20 and B24N24 tube structures are more stable than their square-hexagon alternants by 18.6 and 2.

Stability of carbon-nitrogen cages in fourfold symmetry.

Molecules consisting entirely of nitrogen have been studied extensively for their potential as high-energy density materials (HEDM). Many nitrogen molecules previously studied have low-energy dissociation routes and are therefore too unstable to serve as practical HEDM. However, the incorporation of heteroatoms into a nitrogen structure can have stabilizing effects.

Stability of Carbon-Nitrogen Cages in 3-Fold Symmetry.

Molecules consisting entirely of nitrogen have been studied extensively for their potential as high energy density materials (HEDM). One class of potential high-energy nitrogen molecules is the cage of three-coordinate nitrogen. Previous theoretical studies of cages Nx have shown that the most stable isomers are cylindrical molecules with 3-fold symmetry and triangular endcaps, but such molecules are not stable with respect to dissociation.

The structure and stability of B36N36 cages: a computational study.

The structure and stability of 22 B36N36 cage molecules containing four-membered (F4), five-membered (F5), six-membered (F6), eight-membered (F8) and 12-membered (F12) rings have been computed at the B3LYP/6-31G* level of density functional theory. The most stable structure (1) has T(d) symmetry with six F4 and 32 F6 rings, following the isolated square rule, while the fullerene-like structures (12 F5 and 26 F6) and also structures with F8 and F12 are much higher in energy. Figure The T(d) symmetrical structure (1) with six F4 and thirty-two F6 rings is the most stable B36N36 cage.

Stabilization of Cylindrical N12 and N18 by Phosphorus Substitution.

Molecules consisting entirely or predominantly of nitrogen are the subject of much research for their potential as high energy density materials (HEDM). The problem with many such HEDM candidates is their instability with respect to dissociation. For example, a low-energy dissociation path has been shown for a cylindrical cage isomer of N12.

What makes an N12 cage stable?

Much recent attention has been given to molecules containing only nitrogen atoms. Such molecules N(x) can undergo the reaction N(x) --> (x/2)N(2), which is very exothermic. These molecules are potential candidates for high energy density materials (HEDM).