First-principles study on the electronic structures of the ladder compound NaV2O4F
梯形化合物NaV2O4F电子结构的第一性原理研究

The electronic structures of ladder structural compound NaV2O4F are studied by first-principles calculations with pseudo-potential plane-wave method and spin-polarized generalized gradient approximation (GGA) based on density functional theory (DFT). Four possible spin-ordered states are simulated and the calculated results reveal that the magnetic ground state of NaV2O4F is the antiferromagnetic (AFM) state with AFM interactions both inside the rungs and along the ladder legs. The insulating behavior is successfully simulated with a band gap of about 1.0eV. According to crystal-field theory, the dxy orbitals of V atoms located in the VO4F pyramids have the lowest energy and are split from other d orbitals. The covalent interaction on the rungs becomes weak with the presence of F-ions. Using the calculated total energies for the various spin-ordered states of NaV2O4F, the spin exchange coupling constants are fit out with Noodleman's broken symmetry method. The calculated results indicate that there are ferromagnetic(FM) interactions between the ladders with competitive strength to that on the rungs and thereby NaV2O4F may not be a spin-ladder material.