ELECTRONIC-STRUCTURE OF LAYERED OXIDES CONTAINING M(2)O(7) (M=V, NB) DOUBLE OCTAHEDRAL SLABS

The electronic structure of M(2)O(7) double octahedral slabs with low d electron counts has been studied. It is shown that the nature of the low d-block bands is strongly dependent on the d electron count and t he distortions of the layer. All d(1) systems are expected to be simil ar and to exhibit Fermi surfaces which result from the superposition o f both one-dimensional (1D) and two-dimensional (2D) contributions. Fo r lower d electron counts the electronic structure is quite sensitive to the existence of M-O bond alternations perpendicular to the layer a nd off-plane distortions of the equatorial O atoms. The Fermi surface of these systems can either be purely 2D or have 1D and 2D portions li ke those of the d(1) systems. It is suggested that the recently report ed phase Rb2LaNb2O7 could be a 2D metal. It is also proposed that chem ical reduction of the A'[A(n-1)Nb(n)O(3n+1)] Dion-Jacobson phases with n = 3 could lead to metallic conductivity, in contrast with the resul ts for the n = 2 phases.