Revised crystal structure model of Li2NH by neutron powder diffraction

TL;DR

This study used neutron powder diffraction to propose a revised crystal structure model for lithium imide Li2NH, revealing a face-centered cubic structure with partially occupied hydrogen sites and similarities to lithium amide LiNH2.

Contribution

The paper presents a new crystal structure model for Li2NH based on neutron diffraction data, highlighting hydrogen atom positions and structural similarities to LiNH2.

Findings

Li2NH has a face-centered cubic structure with partial hydrogen occupancy.

Hydrogen atoms are at the 16e site with a specific occupancy pattern.

The N-H distance and H-N-H angle are similar to those in LiNH2.

Abstract

We performed neutron powder diffraction experiments on lithium imide Li2NH, and have proposed a revised crystal structure model. Li2NH has a face-centered cubic structure with a partially occupied hydrogen site. Of the possible crystal structure models that represent the obtained data, the model with F-43m symmetry having hydrogen atoms at the 16e site, in which only one hydrogen atom randomly occupies one of the four hydrogen positions around a nitrogen atom, is most probable. For this model, the distance between the nearest nitrogen and hydrogen atoms is 0.82(6)A, and the angle between H-N-H is 109.5deg., which are close to those of the lithium amide LiNH2, indicating that the structural circumstances around nitrogen and hydrogen are similar in Li2NH and LiNH2.