5d and 4f electron configuration of CeB₆ at 340 and 535 K

Abstract

X-ray atomic orbital (XAO) analysis revealed that at both temperatures the electrons are transferred from B 2p(x)(= p(y)) to Ce 5d and 4f orbitals. At 340 K 5d(j = 5/2)Gamma(8) orbitals are occupied partially, but 4f(j = 5/2)Gamma(8) orbitals are more populated than 4f(j = 5/2)Gamma(7) orbitals, in contrast to our observation at 430 K [Makita et al. (2007). Acta Cryst. B63, 683-692]. At 535 K the XAO analysis revealed clearly that the order of the energy levels of 4f(j = 5/2)Gamma(8) and Gamma(7) states reversed again and is the same as that at room temperature. It also limited the possible 5d configurations to three models among the nine possible ones. However, the XAO analysis could not decide which of the three models was the best with the present accuracy of the measurement. Two of them have partially and fully occupied 5d(j = 5/2)Gamma(7) orbitals and the remaining one has a fully occupied 5d(j = 3/2)Gamma(8) orbital. Since the lobes of 5d(j = 3/2)Gamma(8) or 5d(j = 5/2)Gamma(7) orbitals do not overlap with the 4f(j = 5/2)Gamma(8) orbitals as well as the 5d(j = 5/2)Gamma(8) orbitals, the order of the energy levels of the 4f(j = 5/2) orbitals became the same as that at room temperature. These results indicate that the crystal field varies with temperature due to the electron transfer from B 2p to Ce 5d orbitals. The difference densities after the spherical-atom refinement at the three temperatures clearly revealed the different combinations of 4f and 5d orbitals which are occupied. In the present study positive peaks due to the 4f electrons appear near the Ce nucleus and those due to 5d orbitals are found in the area outside the 4f peaks. Between the two areas there is a negative area distributed spherically at 340 K. The negative area produced by the contraction of 4f(j = 5/2)Gamma(8) orbitals seems to reduce the electron repulsion of the 5d(j = 5/2)Gamma(8) orbitals and helps the 4f(j = 5/2)Gamma(8) orbitals to remain as the ground state.

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

“…4f-EDD was first analyzed by Tanaka, Kato & O " nuki (1997) based on the real 4f orbitals in CeB 6 at 165 K. By employing the complex 4f orbitals which are calculated based on the spin-orbit interaction, the 4f-EDD of CeB 6 was analysed at 100, 165, 230 and 298 K (Tanaka & O " nuki, 2002). In our previous work on CeB 6 (Makita et al, 2007(Makita et al, , 2008 5d orbitals were also occupied above room temperature.…”

“…The ground state of the Sm 3+ ion in free space does not have 5d and 6s electrons. However, since the 5d 5/2 orbitals of CeB 6 were occupied above room temperature (Makita et al, 2007(Makita et al, , 2008, electron populations of 4f 5/2 , 4f 7/2 , 5d 3/2 , 5d 5/2 and 6s 1/2 orbitals were also refined in SmB 6 . Starting from the electron configurations of [Xe]4f 5…”

Resonant inelastic x-ray scattering of CeB6 at the Ce L1- and L3-edges

“…7 The electronic structure of CeB 6 has been subjected to many experimental investigations. Various spectroscopic [8][9][10] as well as diffraction techniques 11,12 have been applied. These previous experimental works, however, did not lead to the same conclusions, showing wide discrepancies.…”

“…11 Recent research from their group also shows that the crystal field in CeB 6 varies with temperature because of charge transfer from B 2p to Ce 5d. 12 In this paper, we report measurements of the L 3 -and L 1edge XANES and the corresponding 2p3d (L α1,2 ) and 2s(5p + valence p) (L γ 4 ) RIXS for CeB 6 . The L 3 -edge XANES monitors the transition of Ce 2p 3/2 electrons to the unoccupied Ce 5d orbitals and is sensitive to the oxidation states of Ce.…”

Spectral analysis of resonant x-ray scattering inCeB6under an external magnetic field

“…52 The splitting is expected at least in the hightemperature region. 53 We have checked, however, that such difference modifies little the overall shape of I av ͑͒ while it affects in a subtle way that of ⌬I͑͒. If the latter spectrum would be measured with more precision, the spectral shape can be used to infer the form of the 5d DOS.…”