梯形化合物NaV2O4F电子结构的第一性原理研究

采用基于密度泛函理论(DFT)的第一性原理赝势平面波方法, 通过自旋极化的广义梯度近似(GGA)电子结构计算对梯形化合物NaV₂O₄F进行了研究. 考虑了四种假想的自旋有序态,计算结果表明该化合物的磁基态具有二维反铁磁(AFM)结构, 即沿梯阶和梯腿方向都表现为AFM作用. 能带结构显示NaV₂O₄F为绝缘体材料, 带隙约为1.0eV. 方锥体中的晶体场劈裂使得VO₄F方锥体中的 V^{4+ 关键词： 2O₄F')" href="#">NaV₂O₄F 梯形化合物 第一性原理计算 电子结构}

First-principles study on the electronic structures of the ladder compound NaV2O4F

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 d_xy 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.