采用密度泛函理论(density functional theory,DFT)中的线性缀加平面波结合增强局域轨道(linearized augmented plane wave and the improved local orbital,APW+lo) 的方法研究了新型铁基超导体LaOFeAs,SrFe2As2,CaFe2As2,LiFeAs,NaFeAs和FeSe的晶体结构、磁性以及电子结构.计算结果表明,铁基超导体的超导电性与该类材料的晶体几何构造以及母体的磁性有密切的关联；超导转变临界温度Tc可以随着FeAs4四面体的畸变程度的减小以及[FeAs]层间距L的增大而提高.进一步对电子结构的研究发现,铁基超导体的磁性主要来自Fe原子的磁矩,pd杂化态决定体系的物理性质,且成为铁基超导体的共有特征.
Using density functional theory (DFT) within the scheme of the linearized augmented plane wave and the improved local orbital (APW+lo),we investigated the newly discovered FeAs layered compounds LaOFeAs,SrFe2As2,CaFe2As2,LiFeAs,NaFeAs and FeSe.We report the crystal structures,magnetism,and electronic properties of these Fe-based materials.The results reveal a close correlation of the superconductivity of these FeAs superconductors with the lattice geometry formation and magnetism of their parent compounds.The maximal critical temperatures Tc could simultaneously increase with the decrease of distortion of the FeAs4 tetrahedrons and the increase of interlayer distance L between two [FeAs] layers.We have further found that the magnetism is mainly attributed to Fe moment,and As 4p and Fe 3d hybrid states affect the physical natures,which are the common feature in these Fe-pnictide superconductors.
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