Chemists and physicists from Russia and other countries have found a way to create “perfect” all the characteristics of explosives from nitrogen, hafnium or chromium. The substance can be obtained at relatively low pressures, according to an article published in the journal Physical Review B and the Journal of Physical Chemistry Letters.
“This finding returns to one of the Holy Grail in materials science, the search for polymeric nitrogen ideal high-energy material. Our group has produced several works related to polinitridami metals. As it turns out, this is a promising class of high-energy substances that require an order of magnitude lower pressures than pure polymeric nitrogen “- says Artem Oganov, professor of Skolkovo Tech and MIPT.
All good explosives, including TNT and plastids, contain nitrogen. With the explosion of nitrogen atoms are joined in a very stable molecule N2, and a large amount of energy is released. The more nitrogen atoms in the chemical compound and the more unusual linkages them with one another or other atoms, the more energy will be released in the explosion.
For this reason, the most powerful explosive would be a compound in which the nitrogen atoms are present only when cloud explosion forming of pure nitrogen gas and minimal amounts of other compounds. Creating an ideal explosives, which scientists call “polymeric nitrogen”, it was predicted by the American scientist Christian Mayo in the early 90s.
In 2004, the substance was obtained experimentally Russian physicist Mikhail Eremtsom at pressures above one million atmospheres, which eliminates its practical application. Since then, scientists have repeatedly questioned about whether it is possible somehow to reduce the pressure of nitrogen polymerization.
Oganov and his colleagues have found a way out of this situation in another recently discovered class of nitrogen compounds. As a rule, the nitrides of various metals have a high hardness, and Russian scientists counted their properties on the computer, trying to identify the most promising nitrides, comparing them with those of carbon compounds.
It was found that some kinds of nitride in which a plurality of nitrogen atoms are joined in a special way with atoms of chromium, zirconium or hafnium, have unusual energy properties similar to the properties of the polymeric nitrogen.
These compounds, except for small inclusions of metal atoms between the endless “strands” of the nitrogen atoms, are similar in structure to the polymeric nitrogen. At the same time they are formed at relatively low pressures – about 220 thousand atmospheres for hafnium nitride and 150 atmospheres for chromium nitride, which, as noted by Oganov, at times less than the pressure required to obtain a polymeric nitrogen. Moreover, calculations show that these substances can remain in the semistable state and at ambient pressures and temperatures.
“In combination with the other elements of the nitrogen can be polymerized at even lower pressures: polinitrid CrN4 chromium can be obtained by slightly lower pressures, and this is hardly a limit Chemists have long been dreaming of synthesis of polymeric nitrogen in large quantities We have proposed a class of compounds that this dream may be implement, “- concludes Oganov.