Formation of LiFN2 with puckered LiF layers via nitrogen intercalation under high pressure

Abstract

The incorporation of molecular guests into ionic frameworks under pressure can produce host–guest structures inaccessible under ambient conditions. Here, we report the synthesis of an intercalated compound, LiFN2, at 105 GPa and 2100 K using the laser-heated diamond anvil cell technique. In situ synchrotron x-ray diffraction and Raman spectroscopy, combined with first-principles calculations, reveal that nitrogen intercalation transforms the compact, three-dimensional B1 structure of LiF into a layered architecture. Puckered LiF layers extend parallel to the crystallographic ac plane, with individual LiF layers alternating with single layers of N2 molecules along the b axis. This structural transformation is accompanied by a change in electronic properties: whereas LiF is insulating, LiFN2 is predicted to be an indirect-gap semiconductor with a calculated bandgap of 3.7 eV. These findings demonstrate that a close-packed ionic framework can accommodate molecular guests through substantial structural reorganization under extreme conditions, providing insight into pressure-induced intercalation and the formation of layered host–guest compounds.