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N6 (Hexanitrogen) Synthesized for the First Time - Twice As Energy Dense As TNT (nature.com)

(Monday August 04, 2025 @03:54AM (EditorDavid) from the big-bang-theories dept.)


Slashdot reader [1]ffkom writes:

> The air around you mostly consists of nitrogen

[2]78%

. And in that air exist happy little monogamous pairs of two nitrogen atoms per molecule, also known as N2. Researchers from the University of Giessen, Germany, recently [3]managed to synthesize N6 molecules , "the first, to our knowledge, experimentally realized neutral molecular nitrogen allotrope beyond N2 that exhibits unexpected stability."

>

> And these appear to be pretty angry little molecules, as they detonate at more than twice the energy density than good old TNT:

>

> A kiloton of N6 is 1.19×10**7mol, which can release an energy of 2.20×109kcal (9.21terajoules) based on the enthalpy. Considering that the standard kiloton TNT equivalent is 4.184terajoules, N6 can release 2.2 times the energy of TNT of the same weight. On the basis of the [4]documented TNT equivalent based on weight for HMX (1.15) and RDX (1.15), N6 can release 1.9 times the energy of HMX or RDX with the same weight.

>

> In interviews the researchers contemplated the [5]possibility of using N6 as rocket fuel , given its superior energy density and that its reaction product is just N2, so basically air, but no smoke, no CO2 or other potentially harmful substances.



[1] https://slashdot.org/~ffkom

[2] https://climatekids.nasa.gov/10-things-air/

[3] https://www.nature.com/articles/s41586-025-09032-9

[4] https://pubs.aip.org/aip/jcp/article-abstract/87/10/5968/93966/Quadratic-configuration-interaction-A-general?redirectedFrom=fulltext

[5] https://www.acsh.org/news/2025/06/27/perfect-rocket-fuel-no-fires-no-chemicals-just-energy-49569



Really cool, application to rockets not so much (Score:5, Informative)

by JoshuaZ ( 1134087 )

People have been trying to synthesize N6 for about a hundred years. In that regard it is similar to trying to synthesize tetrahedrane [1]https://en.wikipedia.org/wiki/Tetrahedrane [wikipedia.org]. But people also synthesized cubane a while ago [2]https://en.wikipedia.org/wiki/Cubane [wikipedia.org] and attempts to make it large enough quantities for rockets were not successful. In the 1960s through the 1980s there was a general tendency to want to have really extreme substances and use them either as rocket fuels or rocket oxidizers. FOOF [3]https://en.wikipedia.org/wiki/Dioxygen_difluoride [wikipedia.org] and ClF3 [4]https://en.wikipedia.org/wiki/Chlorine_trifluoride [wikipedia.org] are the two most infamous ones, and both of those are really easy to synthesize, but just insanely dangerous.

However, one of the major insights in rocket development in the last 25 years has been that even if you can get a few percentage points more of energy out of a rocket fuel, if the fuel or oxidizer is really hard to make or really hard to safely use, then the difficulties involved just aren't worth it. Thus, the cheaper, more reusable rockets were now seeing like SpaceX's Falcon 9 and Rocket Lab's Electron use fuels like kerosene and methane. N6 seems like it would not fit in this paradigm unless someone comes up with a really efficient synthesis method.

That's all the more the case because twice as energetic as TNT isn't that energetic. Methane has a specific energy about 10 times that as TNT. TNT is really good as an explosive not as much because of its high energy but because it easily releases it all at once. So if N6 does get a use, it might be for making missiles and bombs.

[1] https://en.wikipedia.org/wiki/Tetrahedrane

[2] https://en.wikipedia.org/wiki/Cubane

[3] https://en.wikipedia.org/wiki/Dioxygen_difluoride

[4] https://en.wikipedia.org/wiki/Chlorine_trifluoride

Re:Really cool, application to rockets not so much (Score:5, Insightful)

by Retired Chemist ( 5039029 )

The amount they made would be just enough to be dangerous to the synthesizer and that is about it. This is another material that really has no practical use, even if it is non-polluting.

Re: (Score:3)

by JoshuaZ ( 1134087 )

Yeah, but that by itself doesn't tell as that much. A lot of high temp superconductors were first synthesized in very tiny quantities and people later figured out how to synthesize them more efficiently, to the point where a lot them now can even be made in a decent quantity in a high school chem lab. And if this does turn out to be useful as an explosive (which requires it to not just be able to make a big boom but also to not want to go boom too easily) then my naive guess is that a fair bit of research i

Re:Really cool, application to rockets not so much (Score:4, Informative)

by Retired Chemist ( 5039029 )

The basic issue with high energy compounds is that they require energy to produce. There is no free lunch. Add to that the starting materials are even less stable than the product, and I have strong doubts that the material could ever have enough advantages over existing ones to worth the trouble.

Re:Really cool, application to rockets not so much (Score:4, Interesting)

by NewtonsLaw ( 409638 )

But would it really be non-polluting?

In fracturing its atomic bonds, N6 will likely release most of its energy as heat and we all know that if you heat N2 and O2 enough you end up with all types of oxides including a nasty pollutant called NItric Oxide (NO). I can't see N6 simply disassembling itself neatly into 3(N2) in an oxidative environment such as the earth's atmosphere.

Re: (Score:3)

by serviscope_minor ( 664417 )

TNT is good because not only will it release it's energy all at once, it's not super easy not insanely difficult to make it so so.

By the way, kerosene has been popular for ages, and was used in the Saturn 5 and the ill fated N1.

Re: (Score:1)

by tlhIngan ( 30335 )

Yeah, one of the first explosives is nitroglycerine. (And yes, it's the same stuff used in blood pressure medicine).

But nitroglycerine is very unstable and just looking at it funny can make it go off. That's when Nobel (of prize fame) managed to convert it to TNT, which was far more stable. Though it isn't shelf stable - left alone especially in a hot environment and the TNT starts to decompose into nitroglycerine.

Modern explosives are far less reactive nowadays and often only explode when subject to an ele

Re:Really cool, application to rockets not so much (Score:4, Informative)

by newcastlejon ( 1483695 )

> But nitroglycerine is very unstable and just looking at it funny can make it go off. That's when Nobel (of prize fame) managed to convert it to TNT, which was far more stable. Though it isn't shelf stable - left alone especially in a hot environment and the TNT starts to decompose into nitroglycerine.

I'm not an expert but I'm fairly sure dynamite, of Dynamit Nobel fame, is regular nitroglycerin that has been desensitised by mixing it with diatomaceous earth. The time to worry is when the nitroglycerine starts seeping out of the clay. AFAIK nitroglycerine and TNT are unrelated.

Re:Really cool, application to rockets not so much (Score:5, Interesting)

by RockDoctor ( 15477 )

> dynamite, of Dynamit Nobel fame, is regular nitroglycerin that has been desensitised by mixing it with diatomaceous earth

Various materials have been used, including Kieselgh, the "diatomaceous earth" you mention. It's probably a synthetic zeolite mineral these decades, because the natural product is more expensive. But Dynamite per se is much less popular for general explosive use in favour of various other explosives, such as AmFO and synthetic mixtures such as "PowerGel".

> when the nitroglycerine starts seeping out of the clay

On this side of the Pond, we call that "sweating", as in the phrase "porridge oats are good for sweating". See "other materials" above - it's a field expedient worth knowing about for when calling the Bomb Squad isn't such a good option.

> nitroglycerine and TNT are unrelated.

Except by both containing 3 -NO2 "nitro" groups per molecule, introduced by quite similar chemical processes. Hence the name.

Re:Really cool, application to rockets not so much (Score:4, Informative)

by RockDoctor ( 15477 )

> There are also slow and fast explosives, which basically just rate how fast they convert the explosive material into gas.

The measurement is presented in units of a velocity, because it is, at a very basic level, a velocity.

If you made a 1cm by 1cm by 10km long lu-shaped loop sample of TNT, and placed it near a similar length loop of (say) "AN/FO" (ammonium-nitrate/ fuel-oil) and detonated both at one end from the same detonator, the shock waves of the explosives' detonations would arrive separated by around 5 seconds. TNT has a moderately high detonation velocity - around 6900 m/s, while AN/FO maxes out a bit below 5000 m/s. Pure AN has a detonation velocity of about 2500 m/s, while gunpowder, a "low explosive" can be from 0.06 to 9 m/s (depending on the granularity).

Detonation velocity is a useful thing to know if you're trying to design, say, a demolition scheme to bring the centre of a building down onto it's footprint, then collapse the walls in onto the same rubble pile. Which is why "blasting cord" is designed to have a very specific (per brand) detonation velocity.

Re: (Score:2)

by dsgrntlxmply ( 610492 )

Long ago I witnessed a military EOD public demonstration where a 1000 foot roll of det cord was unrolled into a straight line then initiated from one end. You could see the bright light of the detonation travel down the line, a little before the sharp Whoomp arrived (both heard and felt). Also demonstrated: blasting cap in a baseball glove to illustrate the need for caution in handling.

Re: (Score:2)

by ffkom ( 3519199 )

I am somewhat skeptical about the proposed use cases, too. But at least [1]some chemists appear really exited about the results [chemistryworld.com].

[1] https://www.chemistryworld.com/news/most-energetic-molecule-ever-made-is-stable-in-liquid-nitrogen/4021662.article

Re: (Score:2)

by 93 Escort Wagon ( 326346 )

It's technically interesting, so the story does belong here on Slashdot. But, at this moment in time, any talk about potential applications is really putting the cart before the horse.

However that's the life of a university researcher nowadays. No one cares about your great scientific breakthroughs in and of themselves... from day one, you need to be talking about pathways to monetization.

Re: (Score:2)

by dsgrntlxmply ( 610492 )

> I am somewhat skeptical about the proposed use cases, too. But at least [1]some chemists appear really exited about the results [chemistryworld.com].

Prediction: chemists will be exited by trying to reproduce this result.

[1] https://www.chemistryworld.com/news/most-energetic-molecule-ever-made-is-stable-in-liquid-nitrogen/4021662.article

Re: (Score:2)

by ratbag ( 65209 )

Hey Internet pedants, that's how you correct someone's spelling. Well played.

Re:Really cool, application to rockets not so much (Score:5, Informative)

by tragedy ( 27079 )

> That's all the more the case because twice as energetic as TNT isn't that energetic. Methane has a specific energy about 10 times that as TNT.

That's an apples to oranges comparison though. The specific energy of methane that you're using there is almost certainly based on a paradigm where there's free oxygen everywhere to combine with the methane. Presumably, you are comparing a specific energy of 50 to 55 MJ/kg for methane (when burned) to a specific energy of 4.184 MJ/kg for TNT (when detonated). That is, as you said, about an order of magnitude higher than methane when you compare those numbers directly. However, the difference between "when burned" and "when detonated" is significant. TNT does not require any external substances to release energy through detonation. On the other hand, the reaction for methane is CH + 2O CO + 2HO. In other words, every methane molecules requires two oxygen molecules to burn. A methane molecule masses exactly the same as an oxygen molecule (ignoring isotopic variation for simplicity) So, a realistic comparison would be 4.184 MJ/kg for TNT with 16.66 to 18.33 MJ/kg for methane. That's still around 4 times the energy, so, theoretically methane plus oxygen would still be around twice as energy dense.

As you say, it definitely might make more sense as an explosive than a rocket fuel. However, there's more to consider than just the pure energy density for use as a rocket fuel. The above shows that methane plus oxygen would be technically about twice as energy dense by mass than hexanitrogen. However, there are other practical considerations

The most obvious place to start is the fact that methane and oxygen are both gases at room temperature, whereas hexanitrogen is a solid at room temperature. That means major differences in how you handle them. You can either compress the gases, which means very heavy tanks. Typically compressed gas tanks mass something like 5X as much as the gas they hold (don't use propane tanks as a mental example, because that is actually a liquid when compressed) A lot of that mass can be shaved off for applications like rocketry through more exotic composition, and tricks like using spherical tanks (which can hold the equivalent mass of pressurized gas of a cylindrical tank with about half the mass), but those tricks and materials present their own cost and practical concerns. Even then, it is unlikely to be able to use compressed methane and oxygen without adding significant mass, negating the benefit of its high specific energy.

The alternative to compression is using cryogenic liquid. That still presents containment challenges and all sorts of tradeoffs between the mass of extra insulation vs. the structural problems inherent in containing a cryogenic liquid in tanks (not to mention some of the weird behaviors of cryogenic liquids). Plenty of rocket explosions have happened due to the compromises inherent in trying to contain such liquids while keeping the mass under control. The density of liquid oxygen is about 1.14X that of water, while the density of liquid methane is about 0.42 that of water, so the average is about 0.9X that of water. So it is reasonable in terms of volume (which relates to how heavy the rest of the rocket has to be). The density of hexanitrogen, however is about twice that, which can mean that the rest of the rocket can be a lot smaller as well as not needing to either withstand a lot of pressure or require a lot of insulation, or special structural requirements for cryogenic temperatures, or requirements for built in mixers to prevent explosive gas pockets from forming, etc.

I should also mention that you can still use non-cryogenic liquids. Obviously there's kerosene, for example. That still needs an oxidizer though, so that means you're mostly stuck with things like cryogenic oxygen or other gases like nitrous oxide (which can be prone to self-deflagration in large quantities). There are liquid oxidizers that can be used (generally fluorine compounds), but those tend to also

[1]Read the rest of this comment...

[1] https://science.slashdot.org/comments.pl?sid=23759738&cid=65564240

Re: (Score:2)

by JoshuaZ ( 1134087 )

Yeah that's all very valid and good expansions of the complexities of this and does a good job also of articulating a lot of problems with my analysis. My comment is currently at +5 informative, but your comment is a lot better than mine.

Re: (Score:2)

by SoftwareArtist ( 1472499 )

I read the article on using it for rocket fuel, and concluded the author knows a lot less than he thinks he does. Like you said, why would you choose this over methane when it's both less energy dense and much harder to work with? It does have the advantage of not needing an oxidizer, but the energy density still comes out lower even accounting for that.

Then he had this sentence:

> Anything that begins with "According to CCSD(T)/cc-pVTZ (H0) computations" falls under the umbrella of physical chemistry, specifically thermodynamics, a subspecialty so

> beyond comprehension that it makes organic chemistry seem like playing with Legos.

That's wrong on every point. It has nothing to do with physical chemistry and nothing to do with thermodynamics. It's actually

Re: (Score:2)

by Firethorn ( 177587 )

You're right that "easy to handle" is actually a pretty big concern for rockets, which is why we're moving away from hydrogen and more towards methane.

Methane doesn't require anywhere near as cold of a temperature as hydrogen, meaning that a lot of concerns about things like freezing the oxygen goes away, such that while theoretically a hydrogen engine would have more energy and thus thrust by mass, in practical terms, methane often beats it because the rocket itself can be simpler and lighter.

As far as N6

Re: (Score:2)

by BoogieChile ( 517082 )

Surely no discussion about dioxygen difluoride is complete without referencing [1]https://www.science.org/conten... [science.org]

[1] https://www.science.org/content/blog-post/things-i-won-t-work-dioxygen-difluoride

surprisingly stable? (Score:5, Informative)

by serviscope_minor ( 664417 )

I mean given I'd maybe expect it to be marginally stable at LN2 temperatures, that doesn't imply it's particularly stable. More stable than expected is more like survived long enough when treated with extreme delicacy to take a few measurements.

And for rocket fuel you don't generally want something that will happily donate the entire fuel supply with the slightest provocation.

Really this sounds like it would make another fun article in the "things I won't work with" blog under the category of lunatics destroying lab equipment with hilariously unstable compounds consisting of far too much nitrogen.

Props to those lunatics for making it!

Re: (Score:2)

by RockDoctor ( 15477 )

> another fun article in the "things I won't work with" blog

Derek Lowe, currently hosted at Science Mag, for example [1]https://www.science.org/conten... [science.org]

For people of a certain sense of humour, it is utterly, eye-wateringly funny. Otherwise, your kilometrage may vary.

Without RTFA, would I be right in thinking it's the Munich Group of happy laughing pyromaniacs with the leather aprons, armour plate, and light roof?

[1] https://www.science.org/content/blog-post/things-i-won-t-work-dioxygen-difluoride

Nitric acid (Score:2)

by Valgrus Thunderaxe ( 8769977 )

There's an apparatus you can build that will yield [1]HNO3 from air [youtube.com], albeit at a very slow rate.

[1] https://www.youtube.com/watch?v=ep23ds4cZs4

I wonder which of the crazy Youtubers... (Score:3)

by ffkom ( 3519199 )

... will be the first to show the reaction to their audience? Maybe our [1]explosives addict from Australia [youtube.com]? Or [2]the Canadian guy with the many expensive toys [youtube.com]?

[1] https://www.youtube.com/@ExplosionsAndFire/videos

[2] https://www.youtube.com/@NileRed/videos

Re: (Score:2)

by DrMrLordX ( 559371 )

My vote is on Nile. He also has a Blue channel:

[1]https://www.youtube.com/watch?... [youtube.com]

In case you want someone to make pop rocks out of N6.

[1] https://www.youtube.com/watch?v=_uiAcr2449w

Re: (Score:2)

by newcastlejon ( 1483695 )

> My vote is on Nile. He also has a Blue channel:

No I don't think so. Sorry. Nile makes some very good videos but I don't think I've seen him do much in the way of explosives or really complicated chemistry. I'm not saying he couldn't, just that that's not what Nile's channel is about.

Tom of [1]Explosions&Fire [youtube.com] would probably want to but couldn't do it in his shed or on his budget. It would also take two years.

[2]Chemiolis [youtube.com] probably could make it but has far too much sense to try.

[3]PrussianBlue [youtube.com] seems just mad enough to have a go, but I think it's best for all

[1] https://www.youtube.com/@ExplosionsAndFire

[2] https://www.youtube.com/@Chemiolis

[3] https://www.youtube.com/@Prussian_Blue

Re: (Score:2)

by DrMrLordX ( 559371 )

Nile has the budget, you've got to admit. Plus if he wanted to do a collab with the The Slo Mo Guys, they'd probably agree to it. Yeah he'd probably do something stupid with N6 (like make Pop Rocks out of it).

Angry? (Score:2)

by Ossifer ( 703813 )

What have they got to be angry about? They do not even have to be monogamous.

Re: (Score:2)

by 93 Escort Wagon ( 326346 )

For them, a six-way is simply not enough!

Climate change with N6 instead of gasoline (Score:1)

by dicobalt ( 1536225 )

After asking a couple AIs, they seem to disagree which would produce less warming gasses, gasoline, or N6. Apparently N6 yields small amounts of nitrous oxide which has a warming factor of 300x CO2. So even small amounts are troublesome.

Re: (Score:3)

by ffkom ( 3519199 )

Do you really think "AI"s can tell you about a substance that has never been synthesized before?

Re: (Score:2)

by 93 Escort Wagon ( 326346 )

> Do you really think "AI"s can tell you about a substance that has never been synthesized before?

And, right there, you've hit on the fundamental problem with "AI" - what it us actually useful for versus what the wider population (and especially PHBs) think it can do.

Re: (Score:2)

by tragedy ( 27079 )

> Do you really think "AI"s can tell you about a substance that has never been synthesized before?

That is a good point. However, most likely, the AI is just regurgitating a summary of conversations that others have had on the subject. One thing lacking from most current AIs is an up front analysis on the likelihood that the information it is presenting is valid. It could be coming from actual rocket scientists and chemists discussing it somewhere, or from random Joe Schmoes. The standards for academic papers are fairly easily followed by even first year university students and high schoolers (even if wr

Re: (Score:2)

by RockDoctor ( 15477 )

Anything which burns very energetically in air will turn some of the air into (various) oxides of nitrogen.

Most of which are likely to be GHGs to some degree. They have IR-absorption features so they're likely to reduce the IR transmission from Earth's surface to the rest of the universe.

Wikipedia (Score:2)

by timeOday ( 582209 )

Here's the wikipedia page on N6: [1]https://en.wikipedia.org/wiki/... [wikipedia.org]

I can't vouch for it, but at the moment nobody has updated it with the news and it is stated to be "hypothetical." Woohoo! First time I ever beat wikipedia to the punch on anything!

[1] https://en.wikipedia.org/wiki/Hexazine

Wrong compound (Score:2)

by Wdi ( 142463 )

The Wikipedia article refers to a different compound. The one synthesized here is a chain, essentially two N3 azide groups coupled via a slightly bent bond.

So much better than liquid hydrogen... not (Score:3)

by MrKevvy ( 85565 )

So... 9.21 terajoules per kiloton.(Interesting restatement of the more common MJ/kg which is the same numeric value...)

Liquid hydrogen is "only" 13x more energy-dense at 120 MJ/kg, but whereas N6 combusts to N2 which is is plain old air (unless of course it's 100% N2 in which case it's a very up-to-date gas chamber) nasty old hydrogen combusts to dangerous [1]DHMO [dhmo.org] so best to get rid of it.

[1] https://www.dhmo.org/facts.html

Re: (Score:2)

by tragedy ( 27079 )

> So... 9.21 terajoules per kiloton.

As long as we're having fun with units, that would be 2.2 kilotons per kiloton! Note that this is a joke and kilotons and kilotons are different units (depending on context).

Re: (Score:2)

by ravenshrike ( 808508 )

N6 doesn't combust. It detonates and reforms into N2. No oxygen source required. The real question is how sensitive is it to vibration and temperature changes.

re: stability of N6 (Score:1)

by CosineHamster ( 2085234 )

Either it's very stable..or it's a useful explosive. You can't have it both ways. In addition to this..your post does not even indicate what order of bonding occurs in this ostensible "N6" molecules. Give me a link to a molecular formula..

Re: (Score:3)

by JoshuaZ ( 1134087 )

TNT pretty stable. C-4 burns hot but doesn't go boom when set on fire. Ideally explosives are stable except under the exact right circumstances. In fact, one of the major difficulties is balancing these issues. There are a lot of chemicals which are more explosive than the explosives we use but are too unstable to be used in weapons. As for the molecular formula, it is 6 nitrogens in a ring which is depicted in the last article. It is also the form you should guess since nitrogen normally forms two bonds.

Re: (Score:2)

by tragedy ( 27079 )

In military terms, that would be "insensitive munitions". Generally speaking, you want stable explosives for most practical uses. You generally don't want explosives that blow up too easily by dropping, rattling, being heated, being hit with bullets or shrapnel, etc. There's an old french movie: "The wages of fear" ("La saliere de la peur" an adaptation of the french novel of the same name with the novel later being remade as the file "sorcerer") about four truck drivers, desperate for money, driving 2 tru

If it can be mass-produced... (Score:1)

by nichogenius1 ( 9413819 )

... then its biggest bang-for-the-buck application will be fpv drones.

Someone page Derke Lowe! (Score:2)

by morethanapapercert ( 749527 )

Derek Lowe is a drug chemist who has an amusing series of articles dubbed "Chemicals I won't work with".

This seems vaguely relevant [1]https://www.science.org/conten... [science.org]

[1] https://www.science.org/content/blog-post/things-i-won-t-work-hexanitrohexaazaisowurtzitane

He has long since posted about this. (Score:2)

by Wdi ( 142463 )

He already commented twice about this compound, the last one is https://www.science.org/content/blog-post/hexanitrogen-energies

The first post is from June 23. Regardless of this topic popping up on Slashdot now, of course with a sensationalistic slant, it is still yesterdays news for professionals. The paper made a few waves two months ago.

Yay! Finally: sustainable warfare! (Score:1)

by colonel.sys ( 525119 )

Nuff said.

If I promised you the moon and the stars, would you believe it?
-- Alan Parsons Project