La Lu Research Articles

Structural and electronic transformations in quadruple iron perovskite Ca1−xSrxCu3Fe4O12

Crystal structures and electronic transformations of quadruple iron perovskite solid solution Ca1−xSrxCu3Fe4O12 (x = 0.2, 0.4, 0.6, and 0.8) have been investigated by synchrotrons X-ray powder diffraction, Mössbauer spectroscopy, and magnetization measurements. For x = 0.2, a charge disproportionation transition (2Fe4+ → Fe3+ + Fe5+) occur simultaneously with electron charge transfers from Fe to Cu below ∼200 K, as well as CaCu3Fe4O12. In contrast, negative thermal expansions derived from continuous electron charge transfers from Cu and Fe are observed for x = 0.6 and 0.8 at low temperatures below room temperature, as in SrCu3Fe4O12, followed by charge disproportionation transitions. A two-phase coexistence is observed at low temperature below ∼200 K for x = 0.4, indicating that the phase boundary locates in the vicinity of this composition. We have discovered that the Fe–O bond lengths are closely related to their covalency which were estimated from Mössbauer isomer shift parameters. The Fe–O bond covalency plays a crucial role in the types of electronic phase transitions for the Ca1−xSrxCu3Fe4O12 and R3+Cu3Fe4O12 (R: trivalent rare earth metal ions, Y, La–Lu) systems, where the two different low-temperature electronic phases are separated by a common isomer shift value of ∼0.17 mm s−1.

Hydrogen Bonding Dependent Mesoscale Framework in Crystalline Ln(H2O)9(CF3SO3)3

Structurally, hydrogen bonding is identified as a key factor to domain the construction of a crystallographic frame during the crystallization of the Ln(H2O)9(CF3SO3)3 (Ln = La–Lu) system. In situ Raman spectroscopy is used to capture the hydrogen bonding dependent mesoscale frameworks that are formed during Ln(H2O)9(CF3SO3)3 crystallization in aqueous solution by continuously collecting the spectra of structural fragments. The spectral characteristics show that the isolated Ln(H2O)93+ tricapped trigonal prisms cannot exist in the aqueous solution. With the concentration of aqueous solution, the hydrated Ln3+ and CF3SO3– tend to share common H2O molecules, and new hydrogen bonding will be built surrounding Ln3+. Especially, for the Nd, Eu, Yb, and Lu system, Ln(H2O)n(CF3SO3)3 (n = 8–9) clusters instead of hydrated Ln3+ and CF3SO3– are formed in the solution. Under the guiding of intermolecular hydrogen bonds, both bond lengths and bond angles of Ln–O may be regulated, leading to the initial formation of L...

Phase diagrams for the M2MoO4–Ln2(MoO4)3–Hf(MoO4)2 systems, where M = Li–Cs, Tl and Ln = La–Lu

In this paper, the results of systematic studies of complex molybdate systems M2MoO4–Ln2(MoO4)3–Hf(MoO4)2 (M = Li–Cs, Tl; Ln = La–Lu) are presented. Subsolidus phase diagrams of ternary systems were constructed and new triple molybdates were obtained. The optimum synthesis conditions for poly- and monocrystalline form were determined. According to single-crystal data, the structure of one of the representatives of triple molybdates was determined.

Insights into the growth mechanism of REF3 (RE = La-Lu, Y) nanocrystals: hexagonal and/or orthorhombic.

The synthesis of REF3 (RE = La-Lu, Y) nanocrystals with controlled phase structures has so far remained a challenge. Herein we have developed a one-for-all synthetic procedure that allows the successful synthesis of REF3 nanocrystals in a controlled manner. Experimental results showed that the radius of RE ions determines the phase structure: pure hexagonal REF3 (RE = La-Eu), a mixture of hexagonal and orthorhombic REF3 (RE = Gd), and pure orthorhombic REF3 (RE = Tb-Lu, Y) nanocrystals are obtained along with the decrease of the ionic radius. As Gd is positioned exactly in the middle of the lanthanides row, GdF3 nanocrystals were used as a model to further investigate how the molar ratio of F- : Gd3+, the doping of RE ions with different ionic radii, and the doping concentration of certain RE ions affects the crystal structure of the final product.

Extraction kinetics of mixed rare earth elements with bifunctional ionic liquid using a constant interfacial area cell

Extraction kinetics of mixed REEs including La–Lu plus Y except Pm using constant interfacial area cell as equipment and bifunctional ionic liquid as extractant were reported.

Trends in thermodynamic parameters of phase transitions of lanthanide sulfides SrLnCuS3 (Ln = La–Lu)

SrLnCuS3 (Ln = La–Lu) compounds melt incongruently. Their thermochemical parameters are determined. The melting temperatures and the enthalpies of melting are: for SrLaCuS3, T = 1513 K and ΔH = 6.9 kJ mol−1; for SrCeCuS3, T = 1468 K and ΔH = 5.2 kJ mol−1; for SrPrCuS3, T = 1459 K and ΔH = 13.2 kJ mol−1; for SrNdCuS3, T = 1429 K and ΔH = 16.8 kJ mol−1; and for SrSmCuS3, T = 1605 K and ΔH = 2.8 kJ mol−1. Three high-temperature polymorphic transitions are found to occur in SrLnCuS3 (Ln = Sm, Gd–Lu) compounds. The parameters of these transitions are determined: for SrSmCuS3, Tα ↔ β = 1452 K, ΔHα ↔ β = 3.0 kJ mol−1, Tβ ↔ γ = 1464 K, ΔHβ ↔ γ = 0.2 kJ mol−1, Tγ ↔ δ = 1476 K, and ΔHγ ↔ δ = 1.1 kJ mol−1; for SrDyCuS3, Tα ↔ β = 1530 К, Tβ ↔ γ = 1568 К, and Tγ ↔ δ = 1585 K; for SrTmCuS3, Tα ↔ β = 1580 K, Tβ ↔ γ = 1618 K, and Tγ ↔ δ = 1631 K; and for SrYbCuS3, Tα ↔ β = 1567 K, Tβ ↔ γ = 1608 K, and Tγ ↔ δ = 1621 K. The transitions are observed both upon heating and upon cooling. The high-temperature phases are not quenchable. Phase-transition temperature versus r(Ln3+) curves for SrLnCuS3 (Ln = La–Lu) feature the tetrad effect. The SrLnCuS3 (Ln = La–Nd) compounds are classified as thiocuprates; their melting temperatures decrease systematically from La to Nd. The SrCuLnS3 (Ln = Sm, Gd–Lu) compounds are classified as thiolanthanates; their melting temperatures increase in the order from Sm to Tm and from Tm to Lu.

Flux States and Topological Phases from Spontaneous Time-Reversal Symmetry Breaking in CrSi(Ge)Te_{3}-Based Systems.

We study adatom-covered single layers of CrSiTe_{3} and CrGeTe_{3} using first-principles calculations based on hybrid functionals. We find that the insulating ground state of a monolayer of La (Lu) deposited on single-layer CrSiTe_{3} (CrGeTe_{3}) carries spontaneously generated current loops around the Cr sites. These "flux states" induce antiferromagnetically ordered orbital moments on the Cr sites and are also associated with nontrivial topological properties. The calculated Chern numbers for these systems are predicted to be ±1 even in the absence of spin-orbit coupling, with sizable gaps on the order of 100meV. The flux states and the associated topological phases result from spontaneous time-reversal symmetry breaking due to the presence of nonlocal Coulomb interactions.

Structural Systematics for Lanthanide(III) Systems: Interactions of the Achiral Hexamminecobalt(III) Cation with Tris(dipicolinato)lanthanate(III) Anions

Extended structural studies, largely determinations at ~150 K, of the family of hydrates of [Co(NH3)6][Ln(dipic)3] (Ln = La–Lu, and Y; dipic = dipicolinate = pyridine-2,6-dicarboxylate) have provided detailed evidence of the nature of the interactions between the formally achiral cation and the chiral anions. They also provide a reference point for consideration of related systems incorporating chiral cations with and without the capacity to act as H-bond donors.

State of rare earth elements uranyl germanates in aqueous solutions

Uranyl germanates with formula MIII(HGeUO6)3·8H2O (MIII–La–Lu, Y) were investigated in aqueous solutions in the pH range of 0–14. The compounds preserve own structure at pH 3.0–12.0. Out of this interval MIII(HGeUO6)3·8H2O destruct with GeO2, MIII(OH)3 and uranates formation. The compounds solubility changes from 10−7M to 10−3M in the investigated pH range. The MIII(HGeUO6)3·8H2O solubility products(KS), standard formation Gibbs function and solubility curves were calculated, speciation diagrams of U(VI), Ge(IV) and M(III) in saturated solutions and solids were plotted. The lgKS dependence as function of MIII ionic radius has minimum at Gd(HGeUO6)3·8H2O (lgKS(La) = −51.40; lgKS(Gd) = −51.98; lgKS(Lu) = −51.28).

Fractionation characteristics of rare earth elements (REEs) linked with secondary Fe, Mn, and Al minerals in soils

Soil secondary minerals are important scavengers of rare earth elements (REEs) in soils and thus affect geochemical behavior and occurrence of REEs. The fractionation of REEs is a common geochemical phenomenon in soils but has received little attention, especially fractionation induced by secondary minerals. In this study, REEs (La to Lu and Y) associated with soil-abundant secondary minerals Fe-, Al-, and Mn-oxides in 196 soil samples were investigated to explore the fractionation and anomalies of REEs related to the minerals. The results show right-inclined chondrite-normalized REE patterns for La–Lu in soils subjected to total soil digestion and partial soil extraction. Light REEs (LREEs) enrichment features were negatively correlated with a Eu anomaly and positively correlated with a Ce anomaly. The fractionation between LREEs and heavy REEs (HREEs) was attributed to the high adsorption affinity of LREEs to secondary minerals and the preferred activation/leaching of HREEs. The substantial fractions of REEs in soils extracted by oxalate and Dithionite-Citrate-Bicarbonate buffer solutions were labile (10 %–30 %), which were similar to the mass fraction of Fe (10 %–20 %). Furthermore, Eu was found to be more mobile than the other REEs in the soils, whereas Ce was less mobile. These results add to our understanding of the distribution and geochemical behavior of REEs in soils, and also help to deduce the conditions of soil formation from REE fractionation.

Hydrothermal Chemistry and Growth of Fergusonite-type RENbO4 (RE = La–Lu, Y) Single Crystals and New Niobate Hydroxides

A convenient hydrothermal route to high quality single crystals of rare earth orthoniobates RENbO4 (RE = Y, La–Lu) is reported. The title compounds can be grown as single crystals in sizes exceeding 2 mm for most of the rare earths using 30 M KOH at temperatures of 700 °C and pressures of 2 kbar. Single crystal X-ray diffraction shows that they all form in the fergusonite structure type, and the structures were solved in space group C2/c. Examples based on the largest and smallest rare earth ions in the present study include LaNbO4: a = 7.3576(15) Å, b = 11.538(2) Å, c = 5.2128(10) Å, β = 130.900(3)°, Z = 4, R1 = 0.0162, wR2 = 0.0405, and LuNbO4: a = 6.9805(6) Å, b = 10.8271(8) Å, c = 5.0406(4) Å, β = 131.676(3)°, Z = 4, R1 = 0.0178, wR2 = 0.0489. Although domain structures are clearly present in the bulk crystals, the domains are much larger than normally reported from high temperature growth methods, and individual single domain crystals on the order of 0.1–1 mm in size can be selected. Rocking curves of these crystals have narrow fwhm and are Gaussian shaped. Several new phases were also isolated as part of the development of the crystal growth chemistry and were characterized by single crystal X-ray diffraction including such examples as K3YNb2O7(OH)2: P63/mmc, a = 5.9770(12) Å, c = 14.901(2) Å, Z = 2, R1 = 0.0303, wR2 = 0.0765 and CsNb2O5(OH): Fd3̅m, a = 10.5869(14) Å, Z = 8, R1 = 0.0336, wR2 = 0.0741.

Correlation consistent basis sets for lanthanides: The atoms La–Lu

Using the 3rd-order Douglas-Kroll-Hess (DKH3) Hamiltonian, all-electron correlation consistent basis sets of double-, triple-, and quadruple-zeta quality have been developed for the lanthanide elements La through Lu. Basis sets designed for the recovery of valence correlation (defined here as 4f5s5p5d6s), cc-pVnZ-DK3, and outer-core correlation (valence + 4s4p4d), cc-pwCVnZ-DK3, are reported (n = D, T, and Q). Systematic convergence of both Hartree-Fock and correlation energies towards their respective complete basis set (CBS) limits are observed. Benchmark calculations of the first three ionization potentials (IPs) of La through Lu are reported at the DKH3 coupled cluster singles and doubles with perturbative triples, CCSD(T), level of theory, including effects of correlation down through the 4s electrons. Spin-orbit coupling is treated at the 2-component HF level. After extrapolation to the CBS limit, the average errors with respect to experiment were just 0.52, 1.14, and 4.24 kcal/mol for the 1st, 2nd, and 3rd IPs, respectively, compared to the average experimental uncertainties of 0.03, 1.78, and 2.65 kcal/mol, respectively. The new basis sets are also used in CCSD(T) benchmark calculations of the equilibrium geometries, atomization energies, and heats of formation for Gd2, GdF, and GdF3. Except for the equilibrium geometry and harmonic frequency of GdF, which are accurately known from experiment, all other calculated quantities represent significant improvements compared to the existing experimental quantities. With estimated uncertainties of about ±3 kcal/mol, the 0 K atomization energies (298 K heats of formation) are calculated to be (all in kcal/mol): 33.2 (160.1) for Gd2, 151.7 (-36.6) for GdF, and 447.1 (-295.2) for GdF3.

Tuning the ferromagnetic phase in the CDW compound SmNiC2 via chemical alloying.

We report a study on tuning the charge density wave (CDW) ferromagnet SmNiC2 to a weakly coupled superconductor by substituting La for Sm. X-ray diffraction measurements show that the doped compounds obey Vegard’s law, where La (Lu) alloying expands (shrinks) the lattice due to its larger (smaller) atomic size than Sm. In the series Sm1−xLaxNiC2, CDW transition (TCDW = 148 K) for SmNiC2 is gradually suppressed, while the ferromagnetic (FM) ordering temperature (TC) at 17 K slightly increases up to x = 0.3. For x > 0.3, TC starts to decrease and there is no signature that could be related with the CDW phase. Electrical resistivity, magnetic susceptibility and specific heat measurements point toward the possible presence of a FM quantum critical point (QCP) near x = 0.92, where the TC is extrapolated to zero temperature. Superconductivity in LaNiC2 (Tsc = 2.9 K) is completely suppressed with small amount of Sm inclusion near the proposed FM critical point, indicating a competition between the two ordered phases. The tunable lattice parameters via chemical substitution (La,Lu) and the ensuing change among the ordered phases of ferromagnetism, CDW and superconductivity underscores that SmNiC2 provides a rich avenue to study the rare example of a FM QCP, where the broken symmetries are intricately correlated.

Pentavalent Lanthanide Compounds: Formation and Characterization of Praseodymium(V) Oxides

AbstractThe chemistry of lanthanides (Ln=La–Lu) is dominated by the low‐valent +3 or +2 oxidation state because of the chemical inertness of the valence 4f electrons. The highest known oxidation state of the whole lanthanide series is +4 for Ce, Pr, Nd, Tb, and Dy. We report the formation of the lanthanide oxide species PrO4 and PrO2+ complexes in the gas phase and in a solid noble‐gas matrix. Combined infrared spectroscopic and advanced quantum chemistry studies show that these species have the unprecedented PrV oxidation state, thus demonstrating that the pentavalent state is viable for lanthanide elements in a suitable coordination environment.

Tuning the phase, morphology and size of monodisperse ScF3and NaScF4crystals through lanthanide doping

Monodisperse ScF3 and NaScF4 nano-/micro-crystals were prepared by a simple solvothermal method. There were many important factors including the molar ratio of Na/F/(Sc + Ln) and Ln3+ doping to control the synthesis of the products. A phase transformation from monoclinic ScF3 to hexagonal NaScF4 was observed with different molar ratios of Na/F/Sc. Herein, the products doped with 1% Ln3+ (La–Lu, except Pm) demonstrated abundant phases, morphologies and sizes. Moreover, the products with different Lu3+ doping concentrations from 1% to 60% were prepared. The results revealed that different kinds of 1% Ln3+ (La–Lu, except Pm) and diverse concentrations of Lu3+ can modify the phase, morphology and size of the prepared products. A possible formation mechanism for the products with diverse morphologies is proposed. In addition, Ln3+-doped ScF3 or NaScF4 nano-/micro-crystals presented characteristic up/down-conversion fluorescence spectra.

Lanthanide contraction for helicity fine-tuning and helix-winding control of single-helical metal complexes.

Lanthanide contraction was used for helicity fine-tuning and helix winding control of single-helical tetranuclear complexes LZn3Ln (Ln = La-Lu); heavier lanthanides formed a tighter helix with a higher M/P ratio and gave a more abundant partially-coiled structure, resulting in 14-step structural control of the helical complexes.

Thermochemistry study and improved thermal stability of Yb14MnSb11 alloyed by Ln3+ (La–Lu)

Increase in melting points of Yb13.6Ln0.4MnSb11 due to the Ln ordered distribution and ionic bond strengthening.

Crystal chemistry of hydrothermally grown ternary alkali rare earth fluorides.

The structural variations of several alkali metal rare earth fluoride single crystals are summarized. Two different stoichiometric formulations are considered, namely those of ARE2F7 and ARE3F10 (A = K, Rb, Cs; RE = Y, La-Lu), over a wide range of ionic radii of both the alkali and rare earth (RE) ions. Previously reported and several new single-crystal structures are considered. The new single crystals are grown using hydrothermal methods and the structures are compared with literature reports of structures grown from both melts and hydrothermal fluids. The data reported here are combined with the literature data to gain a greater understanding of structural subtleties surrounding these systems. The work underscores the importance of the size of the cations to the observed structure type and also introduces synthetic technique as a contributor to the same. New insights based on single-crystal structure analysis in the work introduce a new disordered structure type in the case of ARE2F7, and examine the trends and boundaries of the ARE3F10 stoichiometry. Such fundamental structural information is useful in understanding the potential applications of these compounds as optical materials.

Spatial variation and provenance of atmospheric trace elemental deposition in Beijing

Atmospheric dry deposition samples were collected in urban and suburban areas of Beijing during a coal-burning period. Chemical characteristics of lanthanoid elements (La–Lu) and five heavy metals (Cr, Co, Mo, Cd, and Pb) were analyzed to determine the variation in spatial scale and deposition provenances. Factor analysis and ternary diagrams were used to identify principle pollution sources. The LaCeSm ternary diagram was used to identify oil refineries using fluid catalytic converters and steel plants, but could not differentiate crustal materials. Lanthanoid characteristic parameters showed similarity between deposition and soil in the local and southwest area in the vicinity of Beijing. Analysis of the five heavy metals enabled discrimination of contaminants originating from human activities. Cd, Pb, and Mo were found to originate from vehicular traffic, whereas Co and Cr originated from industrial emissions and coal combustion. Discriminant analysis established the causes of spatial variation. The result shows that Co, Mo, and Pb can mark the differences between urban and suburban sites. From the PbMoCo plot, it was inferred that the different chemical characters are mainly due to the differing origins of depositions. Deposition samples in suburban areas are principally influenced by soil, chimney soot, and fertilizer, whereas those in urban area are mainly affected by traffic emissions.

ChemInform Abstract: A Family of Rare Earth Molybdenum Bronzes: Oxides Consisting of Periodic Arrays of Interacting Magnetic Units.

AbstractThe compounds LnMo16O44 (Ln: Y, La—Lu) are synthesized from stoichiometric mixtures of Ln2O3, Mo, and MoO3 (silica tubes, 700 °C, 5 d) and characterized by powder and single crystal XRD, magnetic measurements, and DFT electronic structure calculations.