Study of palladium nanoparticles synthesized in alkali borosilicate glass pores by the X-ray line shift method

Metallic Pd synthesized in porous glass with an average pore diameter of 7 ± 2 nm has been studied using the X-ray diffraction and X-ray line shift methods for the first time. The irregular dependence of the reflection width in X-ray patterns on the diffraction angle has been revealed. This can be caused by crystallite growth mostly in the [111] direction or by tetrahedral distortions of the fcc lattice. The shift (difference in energy) of K _α1 lines (ΔE _α1 = 19 ± 2 meV) for nanostructured Pd in comparison with the bulk material is first detected. The detected effect is considered within the assumption of the palladium electron redistribution between Pd 5s- and 4d-bands.     

Specific features of the electronic structure of cerium and its 4d and 5d partners in CeM2 Laves phases (M=Fe, Co, Ni, Ru, Rh, Os, Pt, Mg, Al)

The x-ray line shift method has been used to study the electronic state of Ce (the 4f population) and of its 4d and 5d partners in the CeM₂ Laves phases (M=Fe, Co, Ni, Ru, Rh, Os, Pt, Mg, Al). It is shown that the valence of Ce in CeM₂ decreases monotonically from the limiting value m≈3.35 to m≈3 with decreasing intracrystalline compression of Ce atoms. The population of the outer 4d and 5d orbitals of Ru, Rh, and Os in the Laves phases has been found to be larger than that in metals. Fiz. Tverd. Tela (St. Petersburg) 40, 1397–1400 (August 1998)     

Evolution of the population of outer 6s and 5d shells in rare-earth metals

The shifts of the Kα ₁ and Kβ ₁ lines of all rare-earth (RE) metals (from La to Lu) have been measured experimentally by the x-ray shift method. The population of the RE-metal 6s and 5d shells has been determined by comparing the experimental and theoretical shifts obtained within the Dirac-Fock (Koopmans) model. Trivalent metals exhibit a monotonic cross-over from the 6s ^≈25d ^≈1 to 6s ^≈15d ^≈2 configuration with increasing atomic number. Fiz. Tverd. Tela (St. Petersburg) 41, 1361–1362 (August 1999)     

Influence of parity-forbiddenness in the onset of mixed valence state in Sm1−x GdxS

The electronic structure of Sm and Gd in Sm_1−x Gd_xS has been experimentally studied by the x-ray shift method. Besides the well known strong increase of Sm valence at x≈0.15 (associated with the electronic transition to the mixed valence state), a decrease of Sm valence for x⩾0.9 has been observed for the first time. This phenomenon is explained as due to the 4f-5d hybridization on neighboring Sm atoms involved in the onset of the mixed valence state, and is interpreted as a manifestation of parity violation forbiddenness. Fiz. Tverd. Tela (St. Petersburg) 39, 1017–1019 (June 1997)     

Electronic structure of Rh, Pt, In, and Sn in the mixed-valence systems Eu(Rh1−x Ptx)2 and U(In1−x Snx)3

The electronic structure of Rh, Pt, In, and Sn in the mixed-valence systems Eu(Rh_1−x Pt_x)₂ and U(In_1−x Sn_x)₃ has been studied by the x-ray K line-shift method. It has been found that the occupation of the Rh 4d-shell in Eu(Rh_1−x Pt_x)₂ is higher than that in the metal, and that it grows with decreasing Eu valence (i.e., with increasing 4f-shell occupation). The electronic structure of Pt, In, and Sn in Eu(Rh_1−x Pt_x)₂ and U(In_1−x Sn_x)₃ does not depend on the Eu and U valence and is practically the same as in the metals. These features in the electronic structure of Rh, Pt, In, and Sn in Eu(Rh_1−x Pt_x)₂ and U(In_1−x Sn_x)₃ suggest that the electron released in the f ⁿ → f ⁿ −1+e transitions, rather than transferring to the common conduction band, remains localized at the Eu and U atoms. Fiz. Tverd. Tela (St. Petersburg) 41, 1529–1531 (September 1999)     

Valence instability of uranium in U(Al1−x Gex)3

The electronic structure of U and Ge in the solid solutions U(Al_1−x Ge_x)₃ is investigated by measuring x-ray line shifts. It is shown that uranium has the mixed valence U³⁺ [Rn](5f ³)-U⁴⁺ [Rn](5f ²) over the entire composition range (0⩽x⩽1) and that the population of the uranium 5f shell increases by ∼0.28 5f electrons/U atom from UAl₃ (x=0) to UGe₃ (x=1). The electronic structure of Ge is close to the electronic structure of Ge metal over the entire composition range 0<x⩽1. No variation of the population of the Ge 4p shell is detected to within the experimental error (∼0.1 4p electrons/Ge atom) as the composition varies from x=0.2 to 1. It is established that the delocalization of a U 5f electron occurs as a result of its transition to the s or d band of the same uranium atom. Fiz. Tverd. Tela (St. Petersburg) 39, 1505–1508 (September 1997)     

The Mechanism of 4f-5d hybridization in Sm1−x R x S (R=Ce, Gd, and Y) systems with intermediate valence

For Sm_1?x R _x S (R=Ce, Gd, Y) systems with intermediate valence, the population of Sm 4f states (valence) and populations of Ce 5d, Gd 5d, and Y 4d states are determined by the method of x-ray line displacement. It is found that, in all the systems under investigation, the valence of Sm upon transition to the intermediate valence state increases from m≈2.5 (x≈0.15–0.25) to m≈2.65 (x≈0.8) and then decreases. The populations of Ce, Gd, and Y d states remain nearly constant over the entire region of compositions: $\bar n_d = 0.78 \pm 0.03,0.43 \pm 0.04$ , and 1.07±0.04 for Ce, Gd, and Y, respectively. The experimental dependence of the Sm valence on the composition is explained under the assumption that the 4f electron of an Sm atom can be hybridized through two channels, namely, with the 5d electron of the neighboring Sm atom and with its own 5d electron.     

Effect of annealing temperature on the structure of pyrolysates of diphthalocyanines of rare-earth elements: Neutron research

Small-angle neutron scattering is used to study the structure of carbon matrices—the pyrolysis products of diphthalocyanines with embedded metal atoms (Y, La, and Ce), synthesized at annealing temperatures of 800–1700°C. It is shown that the structure of the porous matrix on the scale of ～10⁰–10² nm is characterized by a level of small pores (3–10 nm in radius) and the next level of the structure is associated with the formation of their aggregates (above 100 nm in size). The quantity and size of the scattering objects increases sharply at annealing temperatures above 1000°C. The results are consistent with X-ray diffraction data.     

Electronic structure of Ce and Sm in hydrides and the 4f collapse in YbHx

The population of the 4f, 5d, and 6s shells of rare-earth atoms in RH_x hydrides (R=Ce, Sm, Yb; x≈2–3) has been studied by the x-ray line-shift method. The population of the 5d and 6s shells of Ce and Sm atoms, and the charge on them in metals and hydrides, were determined from experiment and calculated within the Hartree-Fock-Dirac (Koopmans) model. The decrease of the charge on Ce and Sm revealed upon transition from the metal to the hydride argues unambiguously for the anionic (hydride) model. In YbH_x with x⩾2, the structural transition is accompanied by a strongly pronounced electronic transition from divalent to a noninteger-valence state . Fiz. Tverd. Tela (St. Petersburg) 40, 1393–1396 (August 1998)     

On the electron mechanism of suppression of the magnetic moment of nickel in its alloys with copper and zinc

For the first time, the electronic structure of Ni, Cu, and Zn in Ni_0.27Cu_0.73, Ni_0.18Cu_0.51Zn_0.31, and Cu_0.66Zn_0.34 and some other chemical compounds has been studied using the method of shifts of the K X-ray lines. Statistically reliable shifts (from the positions for the metal) of all diagram K-lines of Ni have been found for both alloys, whereas the shifts of the K-lines of Cu and Zn (also from the positions for the metals) are close to zero for all the alloys. For the first time, estimates have been obtained for the 3d- and/or 4s-facsimiles, i.e., shifts of all diagram lines caused by the removal of one 3d- and/or 4s-electrons. On the basis of these facsimiles, the found shifts of the K-lines of Ni in Ni_0.27Cu_0.73 and Ni_0.18Cu_0.51Zn_0.31 have been explained by the transference of ≲0.10 and 0.15 of its 4s-electron to 3d-band of the same atom.