Novel lithium-nitrogen compounds at ambient and high pressures

TL;DR

This study predicts five new stable lithium-nitrogen compounds at various pressures using ab initio simulations, revealing diverse structures and electronic properties, including pressure-induced metal-insulator transitions.

Contribution

The paper introduces five novel Li-N compounds with unique structures and electronic behaviors, expanding understanding of lithium-nitrogen chemistry under pressure.

Findings

Predicted five new stable Li-N compounds at 0-100 GPa.

Discovered pressure-induced metal-insulator transitions in Li-N compounds.

Resolved previous controversies regarding Li2N2.

Abstract

Using ab initio evolutionary simulations, we predict the existence of five novel stable Li-N compounds at pressures from 0 to 100 GPa (Li13N, Li5N, Li3N2, LiN2, and LiN5). Structures of these compounds contain of isolated N ions, N2 dimers, polyacetylene-like N chains and N5 rings, respectively. The structure of Li13N consists of Li atoms and Li12N icosahedra (with N atom in the center of the Li12 icosahedron) such icosahedra are notdescribed by Wade-Jemmis electron counting rules and are unique. Electronic structure of Li-N compounds is found to dramatically depend on composition and pressure, making this system ideal for studying metal-insulator transitions. For example, LiN3 undergoes a sequence of pressure-induced transitions: metal-insulator-metal-insulator. This work resolves the previous controversies of theory and experiment on Li2N2.