First-principles electronic structure calculations of R₃Al₅O₁₂ (R being the rare-earth elements Ce–Lu)

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• 作者：G. Pari ; A. Mookerjee and A.K. Bhattacharya
• 关键词：Garnets ; Rare-earth dopants
• 刊名：Physica B
• 出版年：2005
• 出版时间：2005
• 年：2005
• 卷：365
• 期：1-4
• 页码：163-172
• 全文大小：353 K

文摘

The paramagnetic electronic structure calculations of the R₃Al₅O₁₂ (R=Ce–Lu, the rare-earth elements) systems by substituting Y atoms in with R atoms, using the tight-binding linearized muffin-tin orbital (TB-LMTO) method within local density approximation (LDA) have been reported. Our calculated band structure and density of states (DOS) for the doped systems clearly show that the ground state of the R=Ce–Yb systems are metallic while the R=Lu system (it has completely filled 4f states) is insulating. This insulating phase of Lu₃Al₅O₁₂ is in very good agreement with the experimental results. Our calculations correctly brings out the narrow bandwidth feature of 4f states. Our studies clearly show that the position of the O-2s/p in YAG remains intact while substitution, the O-2p and R-4f energy gap remains almost the same up to near half filling of 4f states (R=Ce–Pm), from then it decreases continuously up to R=Yb and finally it becomes zero for R=Lu (insulator) due to a strong hybridization between the O-2p and Lu-4f states. Our calculated cohesive energy (E_coh) per molecule for these systems decreases from R=Ce–Sm (up to half filling of 4f bands) then increases from R=Sm–Tb, decreases from R=Tb–Yb (more than half filling) and finally increases for cd82b2e882f22cc161c0a565b715e14"" title=""Click to view the MathML source"">R=Lu, which is an insulator. This decreasing and increasing trend of E_coh is exactly similar to that of the rare-earth elemental solids, indicating that the rare-earth elements in the YAG system plays crucial role in deciding the physical properties of the doped systems. However, there are no experimental results available to our knowledge to compare our results.