Europhys. Lett.
Volume 64, Number 5, December 2003
Page(s) 682 - 688
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 01 November 2003
DOI: 10.1209/epl/i2003-00280-2
Europhys. Lett., 64 (5) , pp. 682-688 (2003)

The metal-insulator transition of the Magnéli phase $\chem{V_4O_7}$: Implications for $\chem{V_2O_3}$

U. Schwingenschlögl, V. Eyert and U. Eckern

Institut für Physik, Universität Augsburg - 86135 Augsburg, Germany

(Received 10 July 2003; accepted in final form 10 September 2003)

The metal-insulator transition (MIT) of the Magnéli phase $\chem{V_4O_7}$ is studied by means of electronic-structure calculations using the augmented spherical wave method. The calculations are based on the density-functional theory and the local density approximation. Changes of the electronic structure at the MIT are discussed in relation to the structural transformations occurring simultaneously. The analysis is based on a unified point of view of the crystal structures of all Magnéli phase compounds $\chem{V}$ n $\chem{O}$ 2n-1 ( $3\leq n\leq 9$) as well as of $\chem{VO_2}$ and $\chem{V_2O_3}$. This allows to group the electronic bands into states behaving similarly 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 $\chem{V_4O_7}$, a strong influence of metal-metal bonding across octahedral faces is found for states both parallel and perpendicular to the hexagonal $c_{\ab{hex}}$-axis of $\chem{V_2O_3}$. 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 $\chem{V_2O_3}$.

71.20.-b - Electron density of states and band structure of crystalline solids.
71.27.+a - Strongly correlated electron systems; heavy fermions.
71.30.+h - Metal-insulator transitions and other electronic transitions.

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