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 the distortions of the layer. All d(1) systems are expected to be similar and to exhibit Fermi surfaces which result from the superposition of both one-dimensional (1D) and two-dimensional (2D) contributions. For lower d electron counts the electronic structure is quite sensitive to the existence of M-O bond alternations perpendicular to the layer and 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 like those of the d(1) systems. It is suggested that the recently reported phase Rb(2)LaNb(2)O(7) could be a 2D metal. It is also proposed that chemical reduction of the A'[A(n)()(-)(1)Nb(n)()O(3)(n)()(+1)] Dion-Jacobson phases with n = 3 could lead to metallic conductivity, in contrast with the results for the n = 2 phases.