The rare earth hexaboride (RE)B₆ series of compounds (RE = Ce, Pr, Nd, Pm, Sm, Eu, Gd) was investigated using the first‐principles approach for exploring new topological insulators. The calculated structural, electronic, and magnetic properties of the materials are discussed in detail. To account for better f‐electron correlation, the Hubbard correction was also tested to correct the Kondo states. The lattice appeared contracted for materials from CeB₆ to GdB₆, and charge is transferred from RE to boron. The inspection of band structure points to spd hybridization between RE‐5d and B‐2s, 2p states at Fermi level. The application of spin‐orbit coupling revealed the conversion in the parity, and an odd number of Dirac cones is found at Γ and X points without Kondo mechanism. PrB₆, GdB₆, and PmB₆ revealed a dispersive conic region near the Fermi level at high symmetry points, which enclosed Kramer's degenerate points with surface states of opposite parity. These materials prove to be a strong topological Kondo insulator with an SmB₆‐like cubic structure without involvement of f‐orbitals in the formation of a Dirac cone. The Hubbard U parameter determined from atomic calculation of RE f‐orbital, apart from the few cases when f‐states remain close to the Fermi level, revealed that the band structures are semimetallic in most cases.

中文翻译：

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稀土稀土六硼化物的f轨道相关能带拓扑的第一性原理研究

使用第一性原理研究了六溴化稀土（RE）B ₆系列化合物（RE = Ce，Pr，Nd，Pm，Sm，Eu，Gd），以探索新的拓扑绝缘体。详细讨论了材料的计算结构，电子和磁性。为了说明更好的f电子相关性，还对Hubbard校正进行了测试以校正Kondo状态。从CeB ₆到GdB _6的材料，晶格出现收缩，电荷从RE转移到硼。带结构的检查表明RE- 5d和B- 2s，2p之间存在spd杂交费米州。自旋轨道耦合的应用揭示了奇偶性的转换，并且在没有Kondo机制的Γ和X点发现了奇数个Dirac锥。PrB ₆，GdB ₆和PmB ₆在高对称点处显示了一个位于费米能级附近的弥散圆锥区域，该区域将Kramer的简并点用相反的奇偶性表面状态包围。这些材料被证明是具有SmB ₆样立方结构的强拓扑近藤绝缘子，而在Dirac锥的形成中不涉及f轨道。根据RE f‐的原子计算确定的Hubbard U参数除了少数情况下，当f态保持接近费米能级时，轨道表明，在大多数情况下，能带结构是半金属的。