# Direct observation of V-trimers in the crystal structure of LiVO2

## TL;DR

The paper reports the crystal structure of LiVO2 and Li0.91VO2, revealing stable V-trimer patterns and resolving long-standing questions about their structural properties.

## Contribution

The study provides the first direct crystal structure determination of the trimerized phase of LiVO2 using X-ray diffraction.

## Key findings

- LiVO2 and Li0.91VO2 crystallize as distinct polytypes with stable V-trimer patterns.
- Streak-like reflections in LiVO2 are attributed to unit cell doubling, not randomly stacked V trimer layers.
- The crystal structure data enable quantitative modeling of trimerization in LiVO2.

## Abstract

Although a trimerized ground state has been predicted for LiVO2 for over half a century, the direct determination of its crystal structure in the trimerized phase by X-ray diffraction remains elusive. Depending on the cooling process, two distinct structural modifications have been prepared - LiVO2 with streak-like, smeared-out superstructure reflection intensities and Li0.91VO2 with well-separated superstructure reflection intensities. The discovery of well-separated superstructure reflections in Li0.91VO2 enabled us to solve its crystal structure. This motivated us to attribute the streak-like superstructure reflection intensities in LiVO2 to an overlap of reflections due to a unit cell doubling along the c-axis, which contrasts with the previous interpretation of randomly stacked V trimer layers. The availability of the crystal structure data forms a starting point for the quantitative modeling of the trimerization phenomenon in this complex Mott insulator.

LiVO2 has been predicted to exhibit a trimerized ground state, but details concerning its crystal structure have remained elusive. Here, the authors investigate the crystal structure of LixVO2 (x ≈ 1, 0.91) and find that a V-trimer pattern remains stable even when Li is deficient, with the two compositions crystallizing as distinct polytypes.