Sciencemadness Discussion Board

Dipotassium 1,5-di(nitramino)tetrazolate: a high energy salt with outstanding detonation properties

Dany - 12-7-2016 at 14:12

Chemical explosives are substances that contain a large amount of stored energy. When exposed to a stimulus (e.g. heat, shock, friction, etc...) the explosive compound decompose rapidly with the liberation of large amounts of gaseous products such as nitrogen (N2), carbon dioxide (CO2), carbon monoxide (CO), water (H2O) and solid carbon (in the form of graphite or diamond for explosives having negative oxygen balance). A good military explosive, should have high detonation velocity (D) and pressure (P). In a condensed explosive, (D) and (P) are strongly linked to the crystal density (ρ) and the heat of formation (HOF). For many years, scientists have tried to find new explosive molecules which are both powerful and stable. Unfortunately, these two properties are often contradictory and a compromise between the two properties needs to be found. Most high-performance explosives are sensitive toward shock and friction, however, some compounds like TKX-50 [1] and octanitrocubane [2] are an exception. it is also important to note, that after years of experimentation, scientists have realized that most organic explosives containing the elements C-H-N-O have detonation performance equal or smaller than D= 10 km/s and P= 500 kbar. the crystal density of C-H-N-O compounds cannot in theory be larger than 2.1-2.3 g/cm3. Energetic materials systems based only on nitrogen such as homoleptic polynitrogen compounds, although very difficult to synthesize, can be considered as very powerful alternative to C-H-N-O systems. In this thread, we will discuss the synthesis and properties of a new explosive compound called Dipotassium 1,5-di(nitramino)tetrazolate [3]. Dipotassium 1,5-di(nitramino)tetrazolate can be obtained via 4 steps synthesis (see figure below).

Although the synthesis requires the use of reagents which are not readily available such as cyanogen azide (CN-N3) and dinitrogen pentoxide (N2O5), the final product (the dipotassium salt) is very interesting. The measured crystal density of Dipotassium 1,5-di(nitramino)tetrazolate is equal to 2.137 g/cm3. the heat of formation of this compound is -112.4 kJ/mol. The EXPLO5 6.02 thermochemical code was used to calculate the detonation performance of Dipotassium 1,5-di(nitramino)tetrazolate. The detonation velocity and pressure are equal to 10.01 km/s and 522 kbar, respectively. If we compare the experimental or calculated detonation performance of this salt to other known military explosives such as β-HMX, RDX and ε-CL-20 we will find that the dipotassium salt is more energetic but unfortunately, it is also very sensitive. The impact and friction sensitivity (IS) and (FS) of this salt (IS=1 J and FS<5 N) whereas (IS=4 J and FS= 48 N) for ε-CL-20. In conclusion, Dipotassium 1,5-di(nitramino)tetrazolate may find uses as primary explosive.


[1] FISCHER, N., FISCHER, D., KLAPOTKE, T. M., PIERCEY, D. G. & STIERSTORFER, J. 2012. Pushing the limits of energetic materials - the synthesis and characterization of dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate. Journal of Materials Chemistry, 22, 20418-20422.

[2] EATON, P. E., ZHANG, M.-X., GILARDI, R., GELBER, N., IYER, S. & SURAPANENI, R. 2002. Octanitrocubane: A New Nitrocarbon. Propellants, Explosives, Pyrotechnics, 27, 1-6.

[3] FISCHER, D., KLAPÖTKE, T. M. & STIERSTORFER, J. 2015. 1,5-Di(nitramino)tetrazole: High Sensitivity and Superior Explosive Performance. Angewandte Chemie International Edition, 54, 10299-10302.


PHILOU Zrealone - 12-7-2016 at 15:07

Very nice!
Although I put a "bemol" on Klapote's team work...
as written here as a side note:
********AUTO-QUOTE*********** :D;)
Like many writings, the densities and VOD are exagerated or based mainly on thermodynamic calculations (much cheaper than actual testing and measurements whitout the need to synthetise much material (testing may require a kilogram))...this effect is sadly true for all big HEM Klapote's...
Now most follow the rule: "Publish or perish" quality of the work is less because they focus on the quantity.

Lately I have noticed that Klapote's team had made a mistake in most of their publications....they based their detonic calculations onto the density of the molecule at the X-ray diffraction temperature (-100°C) what is not the normal use T°.

In fact by using the density at -100°C you overestimate the density vs at 20°C and all related detonics parameters are thus much higher and looks sensational/promising...

Now since past year they have applied an automatic correction based on dillatation coefficient in a way to extrapolate the density of the crystals from -100°C to the standard temperature... this might look a good idea to reduce the biased density value since contraction or dillatation may be considered linear into a 100°C range (or more for certain compounds).

But it is not a good idea because:
1°) They use a single dillatation coefficient...while each compound and each specific crystaline form has a specific coefficient (sometimes dependant on the axis ... thus anisotropic)
2°) Most compounds tends to srink and increase their density while cooling but it is not always the case!
3°) Some compounds change crystalline form by passing from -100°C to 20°C and this will affect the dillatation coefficient that may change dramatically or even change sign (thus instead of srinkage you get dillatation)

So their calculation are purely indicative and quite uncertain.

*************END OF AUTO-QUOTE************

[Edited on 13-7-2016 by PHILOU Zrealone]

Dany - 12-7-2016 at 22:35


The crystal density of Dipotassium 1,5-di(nitramino)tetrazolate was obtained at 173 K and is equal to 2.177 g/cm3. the 298 K value is 2.137 g/cm3, a difference of only 0.04 g/cm3. This small value will barely affect the calculated detonation performance of condensed explosive. However if there is a source of error in the reported detonation performance, it would most likely comes from the thermochemical code calculations. Detonation performance of C-H-N-O explosives are used to calibrate thermochemical codes. You should expect to obtain good prediction if you use the code to estimate C-H-N-O based explosives performance. Explosives with elements like potassium, lithium, magnesium...are less common and the data set used to calibrate the code do not probably contain more than a few number of C-H-N-O-K compounds. So it is not surprising to get a larger deviation in (D) and (P) for C-H-N-O-K compared to C-H-N-O explosives.


Marvin - 13-7-2016 at 02:43

Interesting but the last step bothers me. Add two potassium ions per molecule, which are just spectators. They do nothing but add dead mass. Why not add two Caesium ions instead and wow us with the crystal density. Or just add osmium metal powder and redo the maths. It does feel like gaming the numbers.

Is explo5 a closed source commercial program?

Dany - 13-7-2016 at 03:00


Potassium hydroxide (KOH) is the cheapest and most available reagent to make the final salt.

EXPLO5 code is commercially available from OZM research, Czech Republic.

The EXPLO5 software costs about 7000 Euros (~7750 U.S dollars).


PHILOU Zrealone - 13-7-2016 at 03:09

Quote: Originally posted by Marvin  
Interesting but the last step bothers me. Add two potassium ions per molecule, which are just spectators. They do nothing but add dead mass. Why not add two Caesium ions instead and wow us with the crystal density. Or just add osmium metal powder and redo the maths. It does feel like gaming the numbers.

Is explo5 a closed source commercial program?

The molecule is a diacid, that's why it takes two KOH to neutralize...
-The tetrazole ring has 1 acidic H
-The -N(NO2)-CO2-CH3 is hydrolysed into -NHNO2 (acidic nitramine) + K2CO3 and CH3OH

I agree with you that the alkaline metals cations, will add a bit of dead weight, but most of all they will take some oxygen as K2O for example. On the other side as Dany explained the alkaline metals explosive are few, and so the effect on detonic parameters of Li, Na, K, Cs are largely uninvestigated.
Would be nice on a theorical aspect to have datas for all those 4 dinitraminotetrazolates to know once and for all if it is beneficial to use Li, Na, K or Cs as better performances owing to ionisability (plasma in the explosion gases), owing to low MW (like for propellant applications or volume expansion) or owing to high MW with direct increase of density...

-Maybe in this case they got chance that owing to its very ionic character the molecule display a very low dillatation coefficient...what is the case of saline compounds.
But the ionic character has its drawback too if the charges attracts and forces the molecules into a less favourable packing (then you may have dillatation while cooling instead of contraction).
-Maybe also they had the chance that the compound doesn't change crystalline form into the T° interval.
-Dillatation coefficients are usually very big for organic only materials (thus most CHON energetic materials); while that of salts is almost similar to the least dillating metals.
-Dillatation coefficients (DC) are inversely related to the melting points (the lower the mp, the higher the dillatation coefficients); also DC of gases > liquids > solids.

I know a lot about DC because it is part of my big file of documents for my stil to come theorem demonstration about polymers as a way to increase density...amongst others like the way to increase the density by cooling the Energetic Material down...theorically at the absolute zero they would have the maximum density (but they would also loose initiability/sensitivity)

Again I say that I would prefer concrete real datas instead of theorical calculated datas ... so to me Klapote's team and other works based on codes and calculation are only purely indicative.
-Estimation of HOF
-Estimation of d via extrapolation of d at another T° via an arbitrary chosen DC
-Estimating codes and equations
It starts to be a lot of estimations (even if expected to be into the +/- 5% range), ... plus, plus, plus and you are off by a lot vs the real values.

[Edited on 13-7-2016 by PHILOU Zrealone]

Marvin - 13-7-2016 at 03:53

You are telling me that a prep that uses cyanogen azide picked potassium hydroxide because it's cheap and widely available?

I guess what I'm partly objecting to is that I have no way of interpreting or testing this compound and probably never will. I don't trust breakthroughs made on the basis of theoretical results, especially when the fitness function is proprietary. I really don't trust things like crystal density for salts, for me this is meaningful for (natural isotopic abundance) CHNO compounds at best. As a primary the potassium is of no importance, but then as a primary it's usefulness will really be determined by things other than EXPLO5 relevant numbers anyway. Potassium is at least environmentally benign.

Our posts crossed, it takes me a long time to write anything. I think we are saying similar things.

[Edited on 13-7-2016 by Marvin]

Dany - 13-7-2016 at 03:54


In the field of energetic materials and in certain cases, your are obliged to make estimations. The experimental determination of the condensed heat of formation (HOF) via combustion calorimetry for every energetic materials is impossible. In many cases it was found that there is large uncertainties on the values of these (HOFs) so quantum mechanical methods are the ideal alternative to estimate chemical and physical properties.

Also, it is impossible to measure the detonation performance for every explosive because some of the newly synthesized explosives are very sensitive (like the Dipotassium 1,5-di(nitramino)tetrazolate) or very expensive or even very complicated to synthesize. Every time you need to make detonation performance measurement you need few hundreds of grams of the tested explosive....Imagine if one is on a mission to synthesize 100-200 grams of the highly sensitive Dipotassium 1,5-di(nitramino)tetrazolate in order to measure it's detonation velocity and pressure... that would certainly be a suicidal act.


PHILOU Zrealone - 13-7-2016 at 07:01

I think the potassium salt has been used because, K is cheap but most of all because often K salts crystallize anhydrous and thus are better suited to get the more dense form, well crystallized and relatively stable but stil succeptible to initiation (by shock, flame or friction)

About the synthesis of 100-200 g of EM, you are preaching an already converted people ;) ...see the first § of my auto-quote into the second post of the tread :D ...
--> testing may require a kilogram.

Stil the nice thing with supersensitive compounds is that you also need much less to perform D2D... so in principle, no need to handle as large diameter charges as for unsensitive EM...what also means less material needed to perform tests -->geometrical Dautriche's VOD determination for example.

Dany - 13-7-2016 at 09:55


Sensitive explosives possess very small critical diameter which enables the use of small quantity to perform detonation performance. In practice, nobody will risk his life to perform such dangerous test with highly sensitive explosive. The Dautriche method is old and is not used anymore. Moreover, the Dautriche method give you an access to detonation velocity only. Today, Fiber-optic detonation velocity (FODV) testing is performed to determine the detonation velocity which is far more accurate than the obsolete Dautriche method. The detonation pressure can be obtained from plate dent test or using Photonic Doppler Velocimetry (PDV).