Electronic structure of the spin-Peierls system NaV2O5

The electronic structure of the spin-Peierls (SP) system NaV2O5 is calculat ed within both the local(-spin)-density approximation and on-site Coulomb c orrelation U correction. The narrow band structure due to the strong deform ation of VO5 pyramids in NaV2O5 indicates the one-dimensional property of t his ladder compound and the quarter-filled V d(xy) orbital character. The S P lattice distortion could be reflected by the result that an assumed dimer ization distortion of 0.15 Angstrom for the V chains opens a tiny gap. The gap is increased up to 0.49 eV in the antiferromagnetic state by the enhanc ed exchange splitting of the d(xy) orbital. A strong correlation correction with U-dd = 2.8 eV gives a d-d transition gap of 0.60 eV and a full spin p olarization of 1 mu(B) for the d(xy) state of the V-V rungs. A good agreeme nt with the angle-resolved photoemission spectrum of NaV2O5 leads us to a c lassification of this compound as a d-d transition insulator rather than a charge-transfer one. [S0163-1829(99)00524-X].