X-ray atomic orbital analysis of 4f and 5d electron configuration of SmB6 at 100, 165, 230 and 298 K

• Published in: Acta crystallographica. Section B, Structural science Vol. 66; no. 3; pp. 292 - 306
• Main Authors: Funahashi, Shiro, Tanaka, Kiyoaki, Iga, Fumitoshi
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England International Union of Crystallography 01.06.2010; Blackwell Publishing Ltd
• Subjects: Atomic physics; Crystallography; Density; electron density; Electrons; Kondo insulator; Orbitals; Orbits; X-ray atomic orbital analysis; X-rays
• ISSN: 0108-7681; 2052-5192; 1600-5740; 2052-5206
• DOI: 10.1107/S0108768110009250

Accurate electron‐density measurement of SmB6 at 100, 165, 230 and 298 K, and X‐ray atomic orbital (XAO) analysis were carried out. The 4f‐electron density around Sm and 5d electron density at ∼ 1 Å from Sm were analysed by XAO analysis. The 5d electron density is due to the electrons of the 5dJ = 5/2Γ8 orbitals which stem from the eg orbitals in the strong field approximation. The change in electron populations of the 5d5/2Γ8 orbitals with temperature is similar to that of the resistivity. Since the conduction band consists of 5d5/2Γ8 and B‐2p orbitals according to band theory, this indicates that the larger populations of the 5d5/2Γ8 orbitals correspond to the larger number of localized electrons and are correlated to the resistivity of SmB6. The occupation of the bulky 5d5/2Γ8 orbitals may be the reason for the elongation of the lattice parameter below 150 K. The 4f7/2Γ6 orbitals are obviously occupied except at 100 K, which seems to be caused by the energy gap between 4f5/2 and 4f7/2 states, which begins to exist between 100 and 150 K, and may represent one of the properties of a Kondo insulator.