The Metal-Insulator Transition of the Magneli phase V_4O_7: Implications for V_2O_3

TL;DR

This study uses electronic structure calculations to analyze the metal-insulator transition in V_4O_7, revealing how structural changes influence electronic states and correlations, with implications for understanding V_2O_3.

Contribution

It provides a unified theoretical framework linking structural and electronic properties of Magneli phases and V_2O_3, highlighting the role of metal-metal bonding and correlations in the MIT.

Findings

Structural changes cause localization of bonding states.

Band narrowing increases electronic correlation effects.

Metal-metal bonding influences the MIT mechanism.

Abstract

The metal-insulator transition (MIT) of the Magneli phase V_4O_7 is studied by means of electronic structure calculations using the augmented spherical wave method. The calculations are based on density functional theory and the local density approximation. Changes of the electronic structure at the MIT are discussed in relation to the structural transformations occuring simultaneously. The analysis is based on a unified point of view of the crystal structures of all Magneli phase compounds V_nO_2n-1 (3 =< n =< 9) as well as of VO_2 and V_2O_3. This allows to group the electronic bands into states behaving similar to the dioxide or the sesquioxide. In addition, the relationship between the structural and electronic properties near the MIT of these oxides can be studied on an equal footing. For V_4O_7, a strong influence of metal-metal bonding across octahedral faces is found for states both parallel and perpendicular to the hexagonal c_hex axis of V_2O_3. Furthermore, the structural changes at the MIT cause localization of those states, which mediate in-plane metal-metal bonding via octahedral edges. This band narrowing opens the way to an increased influence of electronic correlations, which are regarded as playing a key role for the MIT of V_2O_3.