A comparative study of Coulomb-correlated electronic structure of the spin-gapped compound alpha -NaV2O5 in Pmmn and P2(1)mn crystal structure
The paramagnetic, spin-polarized, and LDA+U rotationally invariant, fully self-consistent linear-muffin-tin orbital band structure for the inorganic spin-gapped vanadate alpha-NaV2O5 has been calculated for both centrosymmetric group Pmmn and noncentrosymmetric group P2(1)mn (earlier assignment which is now denied as a room temperature structure) and twosupposed antiferromagnetic orders. A very small band gap solution and magnetic moments on vanadium atoms are obtained in the framework of local-spin-density functional approximation. The LDA+U approach has produced the insulating antiferromagnetic solution with more appropriate energy gaps and magnetic moments. We found that the minimal crystal structure changes produce significant changes in the electronic structure and magnetic properties. Starting from an extended four-band tight-binding model, fitted to the paramagnetic Pmmn bands, the hopping terms relevant for the calculation of exchange parameters of a spatially anisotropic Heise...nberg model are estimated. A new frustrating second neighbour coupling, as well as a pronounced diagonal intraladder hopping term, are found.