Homopolar bond formation in ZnV$_2$O$_4$ close to a metal-insulator transition

TL;DR

This paper investigates how partial electronic delocalization near a metal-insulator transition causes structural instabilities and V-V dimer formation in ZnV₂O₄, linking charge and lattice effects without orbital ordering.

Contribution

It reveals a delocalization-driven mechanism for structural instability and dimer formation in ZnV₂O₄ near the metal-insulator transition, independent of orbital ordering.

Findings

Partial electronic delocalization causes structural instabilities.

V-V dimers form along specific directions.

Mechanism couples charge and lattice degrees of freedom.

Abstract

Electronic structure calculations for spinel vanadate ZnV$_2$O$_4$ show that partial electronic delocalization in this system leads to structural instabilities. These are a consequence of the proximity to the itinerant-electron boundary, not being related to orbital ordering. We discuss how this mechanism naturally couples charge and lattice degrees of freedom in magnetic insulators close to such a crossover. For the case of ZnV$_2$O$_4$, this leads to the formation of V-V dimers along the [011] and [101] directions that readily accounts for the intriguing magnetic structure of ZnV$_2$O$_4$.