A team of researchers from three countries were able for the first time to polymer modification of nitrogen, similar to the structure of black phosphorus. To do this, researchers had to create a pressure of 1.38 million atmospheres. The discovery will help to create new materials with high energy density based on nitrogen. The results of a study published in the journal Physical Review Letters.
One chemical element may form several different compounds allotropic modifications. Carbon, for example, has more than nine confirmed allotropes and over 200 hypothetical. The neighboring element of the periodic system, nitrogen — not many allotropes. Today, the researchers there are about 15 solid modifications of nitrogen, wherein the lattice structure. Among them are three polymer modification cg-N, LP-N and HLP-N.
In these polymers, the nitrogen atoms are connected in the structure of single bonds, and it is about six times weaker than the triple, which can be seen in the molecule of atmospheric nitrogen N2. Such a big difference means that the allotropes of nitrogen with a single bond can be used as materials with high energy density. This is possible due to the fact that when returning to standard temperature and pressure, these modifications will break up into molecular nitrogen, releasing into the environment all the energy that was spend on their education. She, according to the laws of thermodynamics, equal to the difference of the energies of triple and single bonds.
A team of chemists from the UK, Germany and USA under the leadership of Dominic Daniela from the University of Bayreuth found a new modification of solid nitrogen. The material, named bp-N (black phosphorus-N), has a polymeric structure of black phosphorus. As the three allotropic modifications of solid nitrogen, bp-N is formed at a high temperature of approximately 4000 Kelvin, and a pressure of 140 GPA 1.4 million atmospheres.
To synthesize a new type of solid nitrogen, the researchers used a diamond anvil. For a start, they drilled the laser cavity for the sample in ultra-thin rhenium foil. Then the foil was placed between two diamonds and put down the camera, clean gaseous nitrogen at a pressure of about 1200 atmospheres. Then the sample was compressed to 1.22 million atmospheres and heated to 2600 Kelvin. Using x-ray diffraction, the scientists found the substance multiple signals not satisfying any of the known forms of nitrogen. In addition, the researchers noticed the change of colour from black to transparent.