Diamondoid Structure of Polymeric Nitrogen at High Pressures

TL;DR

This paper predicts a stable diamondoid N10-cage structure of polymeric nitrogen at high pressures, which is more energetically favorable than other known phases and could be realized experimentally.

Contribution

It introduces a novel diamondoid N10-cage structure of polymeric nitrogen predicted via density functional theory at high pressures.

Findings

Diamondoid nitrogen is a wide-gap insulator.

It is more stable than cubic gauche and layered Pba2 phases above 263 GPa.

The structure adopts a symmetric body-centered cubic form with N10 cages.

Abstract

High-pressure polymeric structures of nitrogen have attracted great attention owing to their potential application as high-energy-density materials. We report the density functional structural prediction of the unexpected stabilization of a diamondoid (or N10-cage) structure of polymeric nitrogen at high pressures. The structure adopts a highly symmetric body-centered cubic form with lattice sites occupied by N10 tetracyclic cages, each of which consists of 10 atoms and is covalently bonded with its six next-nearest N10 cages. The prediction of this diamondoid structure rules out the earlier proposed helical tunnel phase and demonstrates the high-order nature of polymeric nitrogen at extreme high pressures. Diamondoid nitrogen is a wide-gap insulator and energetically more favorable than the experimental cubic gauche and previously predicted layered Pba2 phases above 263 GPa, a pressure which is accessible to high pressure experiment.