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基于密度泛函理论, 采用广义梯度近似方法 (SGGA+U) 计算分析了SmOFeAs电子结构以及 Ir 掺杂对该体系晶体结构和电子结构的影响. 结果表明, 随着Ir的掺杂, SmOFeAs晶体结构中FeAs层与SmO层之间的耦合增强, 晶体内部所含的铁砷四面体随着Ir掺杂其畸变性程度逐步减小. Fe3d以及As4p杂化轨道对体系电子结构起主要影响作用. Ir掺杂所引入的电子使FeAs层的巡游电子增多、Fe3d轨道中的 dz2轨道离域性增强. 当Ir掺杂量为20%时, 费米面处于电子态密度峰值附近, 费米面急剧变化使该体系的Tc值有所增高, 反映了体系费米能级移动与其超导电性的密切关联性. 计算的电子态密度与XPS所得价带谱实验结果一致, 进一步验证了采用SGGA+U方法其包含修正d轨道局域电子的库仑势, 使得计算结果与实验结果更加接近.Based on the consideration of strong correlation of electrons, we have used density functional theory generalized gradient approximation method SGGA+U to calculate SmFeAsO and Ir doping effects on the lattices and electronic properties. It is found that iridium doping at the Fe site enhances the interaction between FeAs and SmO layers and results in a modification of the FeAs4 tetrahedron. The electronic density of states (DOS) of SmOFe1-xIrxAs is studied by comparing the calculations with the X-ray photoemission spectroscopy experiments (XPS). It is revealed that the Fe 3d and As 4p hybridization orbits dominate the electric properties for SmOFe1-xIrxAs. Ir doping makes the five orbitals of Fe3d all filled. Superconductivity is sensitive to the peak position shifting away from Fermi level. Our VASP SGGA+U calculation provides a better agreement with the experimental results when we use an on-site coulomb energy of U on Fe 3d shell, which is sharply contrasted to the GGA process.
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Keywords:
- GGA+U /
- SmOFeAs /
- lattice /
- electronic properties
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[1] Wen H H, Mu G, Fang L, Yang H, Zhu X Y 2008 Europhys. Lett. 82 17009
[2] Chen G F, Li Z, Wu D, Li G, Hu W Z, Dong J, Zheng P, Luo J L, Wang N L 2008 Phys. Rev. Lett. 100 247002
[3] Ren Z A, Yang J, Lu W, Yi W, Che G C, Dong X L, Sun L L, Zhao Z X 2008 Materials Research Innovations. 12 105
[4] Ren Z A, Yang J, Lu W, Yi W, Shen X L, Li Z C, Che G C, Dong X L, Sun L L, Zhou F, Zhao Z X 2008 Europhys. Lett. 82 57002
[5] Chen X H, Wu T, Wu G, Liu R H, Chen H, Fang D F 2008 Nature 453 761
[6] Kadowaki K, Goya T, Mochiji T, Chong S V 2009 J. Phys.: Conf. Ser. 150 052088
[7] Athena S, Sefat, Ashfia H, Michael A McGuire, Jin R Y, Sales B C, Mandrus D 2008 Phys. Rev. B 78 104505
[8] Sefat A S, McGuire M A, Jin R Y, Sales B C, Mandrus D 2008 Phys. Rev. Lett. 101 117004
[9] Zhang J H, Ma B, Liu S, Liu M 2006 Acta Phys. Sin. 55 4816 (in Chinese) [张加宏, 马荣, 刘甦, 刘楣 2006 55 4816]
[10] Ma R, Zhang J H, Du J L, Liu S, Liu M 2006 Acta Phys. Sin. 55 6580 (in Chinese) [马荣, 张加宏, 杜锦丽, 刘甦, 刘楣 2006 55 6580]
[11] Liu S, Li B, Wang W, Wang J, Liu M 2010 Acta Phys. Sin. 59 4245 (in Chinese) [刘甦, 李斌, 王玮, 汪军, 刘楣 2010 59 4245]
[12] Lebegue 2007 Phys. Rev. B 75 035110
[13] Giovannetti G, Kumar S, Brink J D 2008 Physica B 403 3653
[14] Li B, Xing Z W, Liu M 2011 Acta Phys. Sin. 60 077402 (in Chinese) [李斌, 邢钟文, 刘楣 2011 60 077402]
[15] Li Z C, Lu W, Dong X L, Zhou F, Zhao Z X 2010 Chin. Phys. B 19 026103
[16] Chen Y L, Cheng C H, Cui Y J, Zhang H, Zhang Y, Yang Y, Zhao Y 2009 J. Am. Chem. Soc. 131 10338
[17] Kresse G, Furthmuller 1996 J. Phys. Rev. B 54 169 Kresse G, Furthmuller 1996 J. comput. Mater. Sci. 6 15
[18] Anisimov V I, Zaanen J, Anderson O K 1991 Phys. Rev. B 44 943
[19] Dong J, Zhang H J, Xu G, Li Z, Li G, Hu W Z, Wu D, Chen G F, Dai X, Luo J L, Fang Z, Wang N L 2008 EPL. 83 27006
[20] Kamihara Y, Watanabe T, Hirano M, Hosono H 2008 J. Am. Chem. Soc. 130 3296
[21] Kamihara Y, Hiramatsu H, Hirano M, Kawamura R, Yanagi H, Kamiya T 2006 J. Am. Chem. Soc. 128 10012
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