Preparation of a neutral nitrogen allotrope hexanitrogen C2h-N6 | Hacker News Reader

Preparation of a neutral nitrogen allotrope hexanitrogen C2h-N6

nature.com

39 pointsbilsbie27 comments

The best part is the Methods section, which opens with

> Warning! Silver azide and halogen azides are extremely hazardous and explosive. Such compounds should be handled with utmost care and only in very small quantities (<5 mmol). Appropriate safety precautions (blast screens, face shields, Kevlar gloves, soundproof earmuffs and protective leather clothing) are necessary. Make sure to eliminate static electricity before handling. It is also crucial to avoid friction and light exposure and prevent any contact with metals during sample handling to ensure safety.

That is, please do the synthesis in full armor, in the dark and don't touch anything more than strictly necessary.

Also wear ear protection, because it's still going to go bang.

I like the green energy twist in the intro too. "High-energy materials" is an euphemism chemists engaged in weapons research like to use. I went to some conference talks about high energy materials before, and research presented at those talks was always funded by various defence agencies. But maybe that's just a North American thing, this particular group only acknowledges funding from the innocuous Deutsche Forschungsgemeinschaft.

Can't help but to think of Azidoazide azide when I see azides mentioned

> gas-phase reaction of chlorine or bromine with silver azide, followed by trapping in argon matrices at 10 K

Certainly not a process that can be made simple, safe and efficient for use in a battery: explosives or rocket fuel are the only possible kinds of "clean energy-storage materials".

Note that "C2h" is the symmetry[1] and "N6" is the chemical formula. Yes, 6 Nitrogen in a line, N-N-N-N-N-N with some weird bounds and internal charges, probably a good candidate to "Things I Won't Work With" in https://www.science.org/blogs/pipeline From the article:

> Detonation calculation details

[1] See for example another molecule with a different shape but the same symmetry in https://www.cup.uni-muenchen.de/ch/compchem/geom/sym_C2h.htm...

Isn’t it a ring shape?

No, it's almost linear with a small glitch in the center https://www.nature.com/articles/s41586-025-09032-9/figures/4

That's just 3 nitrogen molecules in a trench coat

With a claymore strapped to their chest!

I know it's a joke, but recently a coworker showed us a preprint about theoretical calculations of long strings of nitrogen. They are very unestable and almost immediately they split into a bunch of N2 molecules. So "just 3 nitrogen molecules in a trench coat" is a good characterization of the situation.

No, they only mentioned that hexanitrobenzene has too small dissociation energy computed, sadly.

Derek Lowe of "Things I Won't Work With" weighs in: https://www.science.org/content/blog-post/hexanitrogen

> Compounds consisting only of the element nitrogen [...] are considered promising clean energy-storage materials

They are not actually serious about this, right?

I feel if that directly acknowledging Klapötke of all people is basically a thinly veiled concession that watever you synthesized is too explosive to even be used as an explosive. As seems to be the case here.

Is there even a remotely possibility for this to be used in any practical application?

Noneteless, impressive paper, and getting that abstract into Nature is basically an achievement on its own already.

I mean... You could use it in space instead of nukes as a propellant. Probably would be safer to make there too.

Not useful otherwise yet unless there's some special synthesis requiring it that cannot be done in any other way.

- "decomposition of N6 into three N2 is exothermic (ΔH₀) by 185.2 kcal mol−1"

That's an impressive amount of energy, 9.2e6 J/kg—on the same order as carbon combustion. Wonder if it's a potential rocket fuel additive (it probably isn't, but fun to ask). By comparison, O₃ is "only" 3.0e6 J/kg above diatomic oxygen.

> "is unlikely to decompose through [quantum mechanical tunneling], with an estimated half-life of N6 of more than 132 years at 77 K (Supplementary Table 4). At 298 K, the computed half-life still amounts to 35.7 ms"

Better hope that fridge doesn't fail.

I guess you could have it as some sort of monopropellant? Have some cryogenically cooled N6 flow to the combustion chamber, where it heats up and self-decomposes. Initially you'd have to have some other form of thermal energy input to start the process but once it's going the heat coming off the reaction will trigger further reactions. One downside would be that you'd have much more trouble cooling the engine. Normal engines use the cold fuel and oxidizer flowing around the bell and the combustion chamber to cool them down, but with N6 heating it up before it hits the reaction chamber might be impractical. It would probably be a Bad Thing if it starts self-decomposing while still in the fuel lines...

You can store it inside the LH2 tank, but you'll need to use it completely before you run out of LH2 or it gets too hot. You might be able to inject it in a cold LH2 feed that doesn't pass by the cooling channels and injects directly into the combustion chamber so any N6 gets flushed into the chamber before the engine runs out of LH2. LH2+N6 needs to flow fast enough it doesn't heat up before it hits the chamber.

Still, one commenter mentioned this is too explosive to be used as an explosive. That kind of warns me against thinking too much about this.

> Here we present the room-temperature preparation of molecular N6 (hexanitrogen) through the gas-phase reaction of chlorine or bromine with silver azide

Hmmm, chlorine and bromine - off to a good start - then we come to silver azide.

"Azide" immediately rings all my Derek Lowe bells, and yeah... it's exactly what you'd expect.

That would be this one: https://www.science.org/content/blog-post/things-i-won-t-wor...

> We're talking high-nitrogen compounds here (a specialty of Klapötke's group), and the question is not whether such things are going to be explosive hazards. (That's been settled by their empirical formulas, which generally look like typographical errors). The question is whether you're going to be able to get a long enough look at the material before it realizes its dream of turning into an expanding cloud of hot nitrogen gas.

> [Nitrogen compounds] are considered promising clean energy-storage materials owing to their immense energy content that is much higher than hydrogen, ammonia or hydrazine, which are in common use, and because they release only harmless nitrogen on decomposition.

What the abstract mentions only sideways is that a key use of these properties is production of explosives - nitroglycerin, trinitrotoluene (TNT) or nitrocellulose (modern gunpowder) come to mind, and indeed, they store a lot of energy. Note all have "nitro" in the name.

At this point I'm not sure you care that only exhaust gas is nitrogen.

Hexanitrogen? Nice, but Octanitrocubane is what GURPS promised for TL9.

Found in the warhead table, yes: this is "cleaner" explosives, but military is not spending billions to safe the environment. But get a higher TNT-equivalent per kilogram.

How many nitrogens do we need to have a chemical primary for a fusion weapon?

I suspect you'd need about 0.013 M total, based on https://en.wikipedia.org/wiki/Brown_dwarf#Deuterium_fusion

Looks like a very tiny lump of metallic nitrogen.

Eventually someone will make this.

Definitely not, the primer also needs to be somewhat stable.

This is one reason that even azides are not used in this capacity anymore, and metallic nitrogen would be orders of magnitude less stable. Not to mention requiring special conditions to not explode, like a laser trap or extreme pressures.

Whatever the conditions, if attained, would lead to a virtually undetectable fusion bomb. Nukes for everyone, yay!

A visible amount of the thing wouldn’t even need the fission part.

While it's true that most explosives use nitrogen-based compounds, only a vanishingly small amount of all nitrogen based compounds are used for military applications. Rough estimates are that about 85% goes to producing fertilizer, most of the rest is for various industrial applications and as a fuel.

Relative to the scale of how much fertilizer humanity uses, there's just not all that much demand for explosives.

The fertilizer is also a very effective explosive used in mining and for some military purposes.

Lots of nitrogen molecules together almost always has a military use, even if it’s not the primary purpose.

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