[en] Useful statistical thermodynamic properties of fifteen octahedral hexafluorides are presented in graphical form. These include: vibrational partition function; populations of low-lying vibrational states; densities of vibrational states; and cumulative vibrational population distributions. Values can be read directly from the graphs with an accuracy consistent with the accuracy of the experimental determinations of the vibrational fundamental frequencies, and the approximate validity of the harmonic oscillator approximation. Hexafluorides of the following elements were studied: S, Se, Te, Mo, Tc, Ru, Rh, W, Re, Os, Ir, Pt, U, Np, and Pu. (U.S.)

[en] The split levels associated with the lowest-lying subterms of the 4f^n-16s² (n=3 endash 14) configurations of lanthanide monofluorides LnF (Ln=Pr endash Yb) were calculated by employing the combined ligand field and density functional theory (CLDT) method recently proposed. The 288 calculated split levels are in excellent agreement with experiment and hence shows that the CLDT method can accurately reproduce the low-lying electronic excited states of lanthanide compounds. To quantitatively describe the low-lying electronic states of a lanthanide compound, therefore, the effective ligand potential must include the Coulomb and exchange-correlation potentials of the compound as well as the pseudopotentials of the ligands. copyright 1998 American Institute of Physics

[en] Certain structures of double and ternary fluorides with Rb, Cs, K, Na, In, Tb, Te, U, Th, etc. cubical, tetragonal, rhombic and monoclinic crystal systems, having cation sublattice with more or less deformed cubical I-cell were analyzed. When dispersing various cations over the sublattice interstitials, a tendency towards mutual isolation of high-charge cations is observed. 17 refs., 5 figs., 1 tab

[en] The development of a heated uranium tetrafluoride target system for the TRISTAN isotope separator to release non-rare gas fission products is presented. Off-line experiments indicated that fluorides of As, Se, Br, Kr, Zr, Nb, Mo, Tc, Ru, Sb, Te, I and Xe could be volatilized, but except for Br, Kr, I and Xe, none of these elements was observed after mass separation in the on-line experiments. The results of the on-line experiments indicated a very low level of hydride contamination at ambient temperature and consequently, uranium tetrafluoride replaced uranyl stearate as the primary gaseous fission product target. Possible reasons for the failure of the heated target system to yield non-rare gas activities are discussed and suggestions for designing a new heated target system are presented

[en] Results of indicating of roentgenograms of compounds and crystal phases MR₂F₇, MRF₄, M₂RF₅ forming in MF-RF₃ (M=K, Rb, Cs, NH₄; R - rare earths) are presented. Indicating is conducted by the methos of least square fit with the use of Powder 2 program. Crystal lattice types and lattice parameters are determined

No abstract available

No abstract available

[en] Removal of volatiles at 243 K from solutions of completely dissolved LnF${}_3$ (Ln=La-Dy and Y) and XeF${}_2$ (molar ratio 1 : 3) in anhydrous HF acidified with an excess of BF${}_3$ resulted in [Ln (XeF${}_2$)${}_3$](BF${}_4$)${}_3$ salts. Isolated solids are stable at 298 K and give similar Raman spectra. [La(XeF${}_2$)${}_3$](BF${}_4$)${}_3$ crystallizes in the monoclinic space group C2/m at 150 K. Each La atom is coordinated with three XeF${}_2$ ligands. Six F atoms provided by six bridging BF${}_4$ units, that connect the neighboring La${}^{3+}$ atoms into columns, complete the nine-fold coordination of each La atom. Chemical reactions carried out in the same way but with molar ratio LnF${}_3$:XeF${}_2$ = 1:1 yielded [Ln (XeF${}_2$)](BF${}_4$)${}_3$ salts (La - Nd). Crystal structures of La and Nd salts are isotypic and crystallize in the monoclinic space group P2${}_1$/m at 150 K (La) and 200 K (Nd). Each Ln center is coordinated by nine fluorine atoms provided by eight BF${}_4$ units and one XeF${}_2$ ligand. The BF${}_4$ groups interconnect the Ln atoms into two-dimensional layers. With molar ratio LnF${}_3$:XeF${}_2$ = 1:2 and the same synthetic approach, only La yielded [La(XeF${}_2$)${}_2$](BF${}_4$)${}_3$ salt. Prolonged pumping of [Ln (XeF${}_2$)${}_n$](BF${}_4$)${}_3$ (n=3, 2, 1) at 298 K or attempts of the isolation at 298 K resulted in products with lower content of XeF${}_2$ or in mixtures of various products. In addition to [Ln (XeF${}_2$)](BF${}_4$)${}_3$ and LnF${}_3$/BF${}_3$ products, the [Ln (XeF${}_2$)]F(BF${}_4$)${}_2$ salts (Ln=La, Nd, Sm, Eu, Tb, Dy and Y) also formed. The crystal structures of LaF(HF)(BF${}_4$)${}_2$ and LaF (BF${}_4$)${}_2$ side products were determined. (© 2021 Wiley‐VCH GmbH)

[en] Using the most recent crystallographic data, the Born-Lande equation was employed to calculate lattice energies of the rare-earth trifluorides. The excellent agreement (<0.5 per cent) observed between these calculated values and the values derived from Born-Haber-cycle calculations based on experimental enthalpies suggest that these trifluorides are essentially ionic in character. Based on the experimentally measured enthalpies of formation of the rare-earth trifluorides and the Born-Lande calculational routine, all the unmeasured enthalpies of formation ΔH⁰sub(f)(MX₃,c,298.15K) can be estimated. The magnitude of the monotonic change of ΔH⁰sub(f)(MX₃) for the rare-earth trihalides series (14 4f electrons) is comparable to the energy change between Sc and Ti in which only one 3d electron is added. This energy change is consistent with the chemical evidence that the electrons in the f-orbitals of rare earths contribute negligibly to the bonding. (author)

[en] A rather simple model of the atomic capture process of heavy negative particles in molecules has proved successful for molecules composed of light elements. This model is now used for molecules containing heavier elements and compared to more elaborate calculations. Circumstances are defined in which the Z-law can be used for capture on the core electrons. The importance of individual molecular properties is stressed. (orig.)