Breakthrough study solves the mysteries of nitrogen’s solid phases

In a groundbreaking study recently featured in the pages of the journal Nature Communications, a team of researchers, spearheaded by the University of Bayreuth, in collaboration with scientists from the University of Edinburgh, UK, and the University of Linköping, Sweden, has unraveled the enigmatic behavior of solid nitrogen, casting a revealing light on its complexities.

Under normal conditions of pressure and temperature, nitrogen exists as a gaseous N2 molecule (N≡N), held together by a formidable triple bond. However, when subjected to extreme pressures, gaseous nitrogen undergoes a remarkable transformation, transitioning first into a liquid and then into a solid state at approximately 2.5 GigaPascals (GPa), equivalent to 25,000 times atmospheric pressure.

For over a century, scientists have probed the solid phases of molecular nitrogen, recognizing that understanding the underlying chemical and physical mechanisms is paramount for advancing our knowledge of solid-state sciences.

The elusive Zeta-N2 phase of nitrogen, residing within the pressure range of 60 to 115 GPa, stands as a pivotal piece of the nitrogen puzzle, holding the key to deciphering its unusual behavior. Despite numerous previous investigations, the crystal structure of Zeta-N2, namely how nitrogen molecules are arranged in this phase, remained a mystery.

This international research team, led by Dominique Laniel (University of Edinburgh) and Natalia Dubrovinskaia and Leonid Dubrovinsky (the University of Bayreuth), harnessed a novel experimental technique developed in Bayreuth to successfully unveil the crystal structure of Zeta-N2.

Their method involved subjecting molecular nitrogen to immense pressures, ranging from 60 to 85 GPa, mirroring conditions found within the Earth’s mantle. Employing laser heating up to temperatures of 2,000°C, they achieved the recrystallization of high-quality, submicrometer-sized Zeta-N2 grains. The crystal structure was meticulously resolved using synchrotron single-crystal X-ray diffraction. Armed with these empirical insights, theoreticians at the University of Linköping (Sweden) delved deeper into the unique process of nitrogen polymerization.

The ramifications of this research stretch beyond nitrogen itself, providing profound insights into molecular transformations occurring under extreme conditions. These findings lay the groundwork for progress in solid-state sciences, materials science, and high-pressure physics. The researchers have advanced the methodologies for scrutinizing the properties of functional materials, including those used in electronics, computer chips, semiconductors, solar cells, batteries, lighting, metals, and insulators.

Source: Bayreuth University

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