INTERLAYER COMMUNICATION IN SOME 2-DIMENSIONAL MATERIALS

Tight binding calculations with an extended Huckel Hamiltonian were used to probe interlayer bonding in four representative compounds. In V2O5, a straightforward interaction exists between the apical oxygen lone pairs and empty z2 orbitals on vanadium in adjacent layers. There exists no covalent bonding between Bi2O22+ and WO42- layers in Bi2WO6 at the prototype geometry. However, when the metal octahedra are tilted and the perovskite layer is shifted in its registry, two relatively strong bonds form between the out-of-plane oxygen atoms in the perovskite layer and bismuth. Here the interaction transfers electron density from the oxygen lone pairs to empty Bi-O sigma* orbitals. This, in turn, creates structural deformations within the Bi2O22+ layer. For LiBiPd2O4, we find covalent interaction between bismuth and palladium. Yet this does not appear to be the case in the topologically analogous Pd3P2S8 structure. The reasons for the differences in covalent interaction are discussed in detail.