Exchange and correlation effects in transition-metal oxides 3dn (n = 4, 5 and 6)

Michel Pouchard (1) , Antoine Villesuzanne (1) , Jean-Pierre Doumerc (1)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

In order to clarify the competition of exchange and correlation energies vs crystal-field stabilisation energy, a simple approach is proposed. The exchange and correlation contributions are described on the base of Brandow and Kanamori's U, U′ and JH parameters. The dependence of the crystal field effect on site distortion has simply been modelled using a linear interpolation between undistorted and fully distorted sites. This approach leads to establish phase diagrams for d4, d5 and d6 cations, allowing us to predict the spin-state stability range depending on exchange (JH), crystal field (Dq) and distortion (k) parameters. It can be used to complement the Extended Hückel Tight Binding calculations of the electronic structure of materials having a noticeable ionic character such as 3d transition-metal oxides, in order to interpret the electronic behaviour, and, particularly, discuss the insulating-vs-metallic character of these oxides.

Mots clés: Exchange; Correlation; Crystal field; Transition metal oxides; Electronic structure; Metal–insulator transitions; Spin-state phase diagrams

Domaines: Matériaux

Michel Pouchard, Antoine Villesuzanne, Jean-Pierre Doumerc. Exchange and correlation effects in transition-metal oxides 3dn (n = 4, 5 and 6). Comptes Rendus. Chimie, 2003, 6 (1), pp.135-145. ⟨10.1016/S1631-0748(03)00014-6⟩. ⟨hal-00200887⟩