First-principles study on the insulating state of α′-NaV2O5

The electronic structure of an inorganic compound with a spin gap alpha'-NaV2O5 has been studied by first principles calculations with the generalized gradient approximation. We have calculated the total energy of the crystal structure with P-mn21 and P-mmn symmetries, respectively, which is still controversial in experiments. Insulating states are reproduced by both antiferromagnetic and ferromagnetic calculations, although metallic states are obtained within the nonmagnetic ones. After structure optimization, the crystal structure with the P-mn21 symmetry is unstable and the optimized atomic positions form the structure with the P-mmn symmetry. The antiferromagnetic state with the P-mmn symmetry has the lowest energy. Our numerical results for the antiferromagnetic case can explain many experimental results of the insulating state of alpha'-NaV2O5 above the charge ordering temperature. [S0163-1829(99)50720-0].