Observation of molecular and polymeric nitrogen stuffed NaCl ionic layers

TL;DR

This study reveals that under high pressure, NaCl reacts with N2 to form layered structures with nitrogen molecules, transforming its electronic properties and enabling nitrogen polymerization, which could inform new material designs.

Contribution

The paper uncovers a novel high-pressure reaction between NaCl and N2, leading to layered structures with nitrogen stuffing and polymerization, expanding understanding of NaCl chemistry under extreme conditions.

Findings

NaCl reacts with N2 to form layered NaCl(N2)2 at 50 GPa

N2 molecules break NaCl into two-dimensional layers

N atoms polymerize into zigzag chains at 130 GPa

Abstract

Sodium chloride (NaCl), a ubiquitous and chemically stable compound, has been considered inert under ambient conditions. Its typical B1 structure is highly isotropic without preferential direction, favoring the growth of a three-dimensional network of strong Na-Cl ionic bonds. Here, we employ first-principles structural searching and synchrotron X-ray diffraction to unravel an unexpected chemical reaction between NaCl and N2 to produce a hybrid salt-NaCl(N2)2, where N2 molecules break the isotropic NaCl structure into two-dimensional layers upon synthesis at 50 GPa. In contrast to the insulating properties of pristine NaCl, the electronic bandgap of the N2-stuffed NaCl narrowed to 1.8 eV, becoming an indirect bandgap semiconductor. Further compression to 130 GPa induced the polymerization of N atoms into zigzag N-chains. Our findings not only demonstrate the possibility of unusual N-chemistry under extreme conditions, but also suggest a feasible approach for the design of layered NaCl frameworks to modulate the polymerization of nitrogen.