Researchers resolve long-standing structural mystery of γ-N2

Nitrogen is one of the simplest molecules in nature, yet its behavior under extreme conditions continues to surprise scientists. For more than half a century, the crystal structure of γ-N₂, a molecular phase of solid nitrogen, remained a subject of debate despite extensive experimental and theoretical investigations.

Recently, a research team led by Prof. LIU Xiaodi from the Hefei Institute of Solid State Physics, Hefei Institutes of Physical Science of the Chinese Academy of Sciences, in collaboration with the University of Edinburgh and other international partners, has provided new insight into this long-standing question by combining high-pressure experiments with first-principles calculations.

The results were published in Matter and Radiation at Extremes.

Using synchrotron X-ray diffraction, Raman spectroscopy, infrared spectroscopy and density functional theory calculations, the team systematically investigated γ-N₂ across a wide pressure-temperature range. Their results provide compelling evidence that γ-N₂ adopts a monoclinic P21/c structure containing two nitrogen molecules per unit cell.

The study supports a long-standing theoretical prediction and improves understanding of nitrogen phases under extreme conditions, according to the team.