【摘要】 密度泛函理论(DFT)方法通常难以处理强关联体系,而DFT+U方法的计算结果强烈地依赖于U的取值.利用一种混合了部分DFT交换关联势和非局域Hartree-Fock精确交换势的杂化泛函HSE方法,研究了钙钛矿锰氧化物的两个典型反铁磁绝缘体CaMnO3和LaMnO3的电子结构,分析了二者的能隙特征与Mn离子价态和磁有序态的关联.根据ZSA方案CaMnO3可划分为电荷转移型绝缘体.LaMnO3的能隙表现出各向异性特征,其中沿c轴方向及ab面内的自旋多数通道中能隙的Mott-Hubbard特征更为显著,而自旋少数通道显示出完全的电荷转移型特征.更多还原

【Abstract】 Density function theory(DFT) method is difficult to treat strongly correlated system,while DFT+U produces U-dependent results.The electronic structures of two typical antiferromagnetic insulators CaMnO3 and LaMnO3 in perovskite manganese oxides were investigated by using the hybrid functional HSE,which combined the DFT exchange-correlation potential and the nonlocal Hartree-Fock exact exchange potential.The relationship among the energy gap nature,the valence states of Mn,the magnetic structure was discussed.The results showed that CaMnO3 is classified as charge-transfer insulator according to ZSA(Zaanen-Sawatzky-Allen) scheme.The energy gap of LaMnO3 shows anisotropic character,in which the Mott-Hubbard character is dominant along c axis and in spin-majority channel within ab plane,while the charge-transfer character is exhibited in spin-minority channel.更多还原