'Black Nitrogen': Researchers Discover New High-Pressure Material and Solve Periodic Table Puzzle
martyb writes:
In the periodic table of elements there is one golden rule for carbon, oxygen and other light elements: Under high pressures, they have similar structures to heavier elements in the same group of elements. But nitrogen always seemed unwilling to toe the line. However, high-pressure chemistry researchers of the University of Bayreuth have disproved this special status. Out of nitrogen, they created a crystalline structure which, under normal conditions, occurs in black phosphorus and arsenic. The structure contains two-dimensional atomic layers, and is therefore of great interest for high-tech electronics. The scientists have presented this "black nitrogen" in Physical Review Letters.
[...] Elements with similar properties are placed one below the other in the same column, and thus form a group of elements. [...] In earlier high-pressure experiments, nitrogen showed no structures similar to those exhibited under normal conditions by the heavier elements of this group-specifically, phosphorus, arsenic and antimony. Instead, such similarities are observed at high pressures in the neighboring groups headed by carbon and oxygen.
In fact, nitrogen is no exception to the rule. [...] At very high pressures and temperatures, nitrogen atoms form a crystalline structure that is characteristic of black phosphorus, which is a particular variant of phosphorus. The structure also occurs in arsenic and antimony. It is composed of two-dimensional layers in which nitrogen atoms are cross-linked in a uniform zigzag pattern.
[...] It took truly extreme conditions to produce black nitrogen. The compression pressure was 1.4 million times the pressure of the Earth's atmosphere, and the temperature exceeded 4,000 degrees
More information: Dominique Laniel et al, High-Pressure Polymeric Nitrogen Allotrope with the Black Phosphorus Structure, Physical Review Letters (2020). DOI: 10.1103/PhysRevLett.124.216001
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