钠锰氧化物高压相变的理论预测

Theoretical Calculations for NaMn_2O_4 Oxide Phase Transition

运用密度泛函(DFT)平面波赝势方法(PWP),计算了钠锰氧化物三种物相的状态方程及其电子结构.研究结果表明:利用状态方程得到的钠锰氧化物从尖晶石型结构的SP相转变为CF相和CT相的相变压强分别为4.94 Gpa和20.48 GPa,CF相与实验值误差仅为+0.44 Gpa.进一步对CT相钠锰氧化物的能带结构和态密度的分析表明钠锰氧化物CT相是一种带隙为2.15 eV的窄禁带半导体材料.靠近费米能级附近的Mn-3d电子轨道和O-2p电子轨道的强烈杂化决定了材料的电子性质.

The equations of state for the three phases of NaMn2O4 oxides are presented by the pseudowaves plane （PWP） approach based on density functional theory （DFT）. The calculated and experimental results are compared and show that the transition pressures from NaMn2O4 spinel to CaFe2 04 -type NaMn2O4 and then to CaTi2O4-type NaMn2O4 are 4.94 GPa and 20.48 GPa, respectively, the differences between calculations and experiment values for CF phase is ＋0.44 Gpa. The electronic properties of CaTi2O4-type NaMn2O4 are investigated by use of DFT. The calculated results indicate that this compound is a semiconductor with a small indirect gap 2.15 eV. It is indicated that the hybrid between Mn3d and O2p orbitals near Fermi level takes part in dominate role to electric properties of this compond.