Lanthanum Atoms Research Articles

New even-parity energy levels of the neutral Lanthanum atom derived from difficult to interpret measurements

We report the discovery of seven even-parity energy levels of the Lanthanum atom. These levels are derived from experimental results which are quite difficult to interpret, since most of the investigated structures appear in complicated blend situations. 17 spectral lines can be classified as transitions in which these levels are involved.Further we could improve the J-values and hyperfine structure constants A of two earlier published levels due to the investigation of additional lines.

Adsorption of adrucil on [La-CTF-0]3+ system for drug delivery by density functional theory

Fluorouracil is a chemotherapy medication used in the treatment of many cancers. Motivated in the development of new drug delivery, in the present work, the adsorption of adrucil drug on [La-CTF-0]+3 was studied. Electron and interaction properties of [La-CTF-0]+3 with the adrucil molecule have been explored by DFT. The optimized structure and energy were investigated usin the PBE0/def2-TZVP method. Results suggest that adrucil molecule can be adsorbed physically on the [La-CTF-0]+3, with adsorption energy of 69.82 kcal/mol. The HOMO-LUMO orbitals of the system indicate that the electron properties of the [La-CTF-0]3+ are slightly altered after the adsorption of the drug on [La-CTF-0]+3. The natural bond orbital calculation shows charge transfer between the electron donor oxygen on adrucil and the lanthanum atom, acceptor. This research provides new insights into the development of drug delivery systems.

LaNiGe with Non‐centrosymmetric LaPtSi Type Structure

The equiatomic germanide LaNiGe was synthesized from the elements by arc‐melting and subsequent annealing at 1173 K for 14 days. Its non‐centrosymmetric LaPtSi type structure was refined from single‐crystal X‐ray diffractometer data: I41md, a = 420.80(6), c = 1440.3(3) pm, wR = 0.0477, 284 F2 values and 14 variables. The nickel and germanium atoms build up a three‐dimensional [NiGe]δ– polyanionic network (2 × 241 and 1 × 242 pm Ni–Ge) in which the lanthanum atoms fill cavities with coordination number 12. This picture of chemical bonding is supported by an evaluation of the electron localization function. Physical properties of LaNiGe were studied by means of magnetic susceptibility, magnetization, specific heat and electrical resistivity measurements. The compound was found to be a Pauli paramagnet with a molar magnetic susceptibility of about χ = 1.6 × 10–4 emu·mol–1·Oe–1. The temperature dependence of the electrical resistivity shows Bloch‐Grüneissen‐Mott behavior indicating the metallic character of LaNiGe, which is in full agreement with the results of electronic structure and density of states calculations. No superconducting transition was observed in the temperature regime down to 1.72 K.

Effect of isovalent substitution on the crystal structure and properties of two-slab indates BaLa2−xSmxIn2O7

AbstractExploring the effect of isomorphic substitution of atoms on crystal structure and features of oxide compounds is one of the main tasks of modern materials science. This paper deals with the La/Sm isovalent substitution in a two-slab perovskite-like BaLa2In2O7 structure and its effect on the structural features and magnetic properties of BaLa2−xSmxIn2O7 indates synthesized. A complete characterization including data of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), structural calculations (Rietveld method), second optical harmonic generation of the laser radiation, calculations of valence bond sums (VBS), and magnetic susceptibility data of phases obtained is presented. The existence region of BaLa2−xSmxIn2O7 solid solutions with a two-slab perovskite-like structure (0 ≤ x ≤ 1.8) was established, and their coordinate parameters were refined. The character of barium and RE atoms distribution in BaLa2−xSmxIn2O7 structure has determined, and the correlation between substitution degree of lanthanum atoms and the length of Ln–O2 interblock distance has revealed. The magnetic properties of BaLa2−xSmxIn2O7 were considered in terms of the crystal field effect.

Influence of halogens on organometallic open pentadienyl lanthanum complexes XLa(C5H7)2 (X = H, F–I)

The electron and structural understanding of metal-coordinated pentadienyl ligands is essential for their subsequent use in different areas of chemistry, especially in the area of organometallic chemistry. Thus, in this work we have analyzed in gas-phase the influence of group 17 elements in complexes formed with the lanthanum atom and the open pentadienyl ligand, XLa(C5H7)2, where X = H, F, Cl, Br, and I. The results, using density functional theory (PBE0/def2-TZVP) and NBO analysis, suggest that all carbon atoms of both ligands are η5 coordinated to the lanthanum atom, and X atoms play a very important role in affecting the electron transfer from the ligands to the central atom due to their electronegativity. In addition, the NBO analysis and the geometry of each structure suggest that the atoms that contribute the most as charge donors to the lanthanum atom are those at the center of the pentadienyl ligand. Energies were computed with the domain based local pair-natural orbital coupled-cluster (DLPNO-CCSD(T)) method.

Lanthanum and strontium modified bismuth ferrite based perovskites with ultra-narrow band gaps

The wide optical band gaps of ferroelectric perovskite oxides have restricted their light absorbing capacities in the photovoltaic devices. In this work, an ultra-narrow band gap E g and wide optical absorption across the ultraviolet-visible-infrared sunlight spectrum was achieved in lanthanum and strontium atoms modified Bi(Fe, Mn)O3 perovskites by chemical substitution and defect engineering. XRD results show that the A and B site co-substituted samples are single phase. The XPS characterizations indicate the Fe ions are in the trivalent state for all the samples. The LM6 and SM6 samples exhibit an ultra-narrow band gap about 1.26 eV and 1.06 eV, respectively. The reduced E g was due to the defect states produced within the band gap, acting as a scaffold to give electrons to Fe 3d states and receive the electrons from O 2p states. Based on this research, these chemically modified BFO based perovskite could potentially extend its sunlight absorption deep into the infrared region.

Single-crystal structure determination of LaNi5–x In x and LaNi9–x In2+x

Abstract The crystal structures of the solid solution LaNi5–x In x (x = 0.51) and the ternary compound LaNi9–x In2+x (x = 0.80) have been investigated by single-crystal X-ray data. The LaNi5–x In x phase is isotypic with CaCu5: space group P6/mmm, a = 5.042(2), c = 4.009(1) Å. The crystal structure investigation of LaNi9–x In2+x (x = 0.80) was performed at T = 295 and 100 K: YNi9In2 type, space group P4/mbm, a = 8.3976(3), c = 5.0439(3) Å for T = 295 K and a = 8.3814(2), c = 5.0352(2) Å for T = 100 K. The lanthanum atoms are located on split positions 2a (0 0 0) and 4e (0 0 0.05).

High-speed visualization of metal oxide precursor in multiphase AC arc during nanoparticle formation

The purpose of the present work is to elucidate the formation mechanism of metal oxide nanoparticles in a multiphase AC arc, which is one of the most attractive thermal plasma sources. Lanthanum oxide nanoparticles were focused on, on the basis of spectroscopic diagnostics and thermodynamic considerations. The dynamic behavior of lanthanum vapor and lanthanum monoxide in a multiphase AC arc was visualized by a high-speed camera through band-pass filter optics. Furthermore, the two-dimensional temperature field of the multiphase AC arc was successfully estimated by the same camera system based on the relative intensity method, which included the emissions from the lanthanum atom and lanthanum ion. The obtained temperature profile and intensity profile of lanthanum and lanthanum monoxide suggest that the oxidation from lanthanum to lanthanum monoxide occurred following thermodynamic equilibrium. Understanding these fundamental phenomena in the thermal plasma nanofabrication process enables one to expand the capability of thermal plasma for innovative material processing.

SrPdGa3 type gallides RERhGa3 with RE=La, Ce and Pr

Abstract The ternary rare earth gallides RERhGa3 with RE = La, Ce and Pr were synthesized by arc-melting and subsequent annealing in a muffle furnace. The gallides were characterized through Guinier powder patterns and the structure of LaRhGa3 was refined from single-crystal X-ray diffraction data: SrPdGa3 type, Cmcm, a = 639.2(2), b = 1030.9(2), c = 589.3(2) pm, wR2 = 0.0964, 416 F 2 values and 19 variables. The rhodium and gallium atoms build up a three-dimensional polyanionic network [RhGa3] which is stabilized through Rh–Ga (245–251 pm) and Ga–Ga (267–295 pm) bonds and filled by the lanthanum atoms. The crystal chemical relationship with the structures of LaRh2Ge2 (ThCr2Si2 type), LaRh2Ga2 (CaBe2Ge2 type) and LaRhGe3 (BaNiSn3 type) is discussed.

Comment on “Measurement of the electron affinity of the lanthanum atom”

The electron affinity of the lanthanum atom was recently measured by slow-electron velocity map imaging in a photodetachment experiment [Y. Lu et al., Phys. Rev. A 99, 062507 (2019)]. Several detachment threshold energies have been measured, which correspond to different energy levels of the initial ion and/or final atom. Only one measurement, however, has been exploited to determine the electron affinity. Applying the ordinary spectroscopic method to the complete set of data presented by the authors, one obtains a slightly different, more precise and more consistent value of the electron affinity of La: $449\phantom{\rule{0.16em}{0ex}}691(17)$ instead of $449\phantom{\rule{0.16em}{0ex}}697(20)\phantom{\rule{4pt}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}$, i.e., $0.557\phantom{\rule{0.16em}{0ex}}546(20)$ instead of $0.557\phantom{\rule{0.16em}{0ex}}553(25)\phantom{\rule{4pt}{0ex}}\mathrm{eV}$.

Highly active Ce, Y, La-modified Cu/SiO2 catalysts for hydrogenation of methyl acetate to ethanol.

Rare earth element (Ce, Y, and La) modified Cu/SiO2 catalysts via hydrolysis precipitation and impregnation method were fabricated for the vapor-phase hydrogenation of methyl acetate to ethanol. LaOx showed the most pronounced promotion in the catalytic tests. After detailed characterizations, via N2 adsorption–desorption, XRD, N2O chemisorption, FTIR, H2-TPR, H2-TPD, TEM, XPS, and TG/DTA, we found that the addition of promoter LaOx can decrease the particle size while in turn, it can increase the dispersion of copper species. The strong interactions between copper and lanthanum atoms alter the surface chemical states of the copper species. This results in the generation of more Cu+ species and high SCu+ values, which are responsible for the excellent activity and stability during hydrogenation. In addition, the content of additive LaOx and reaction conditions (reaction temperature and LHSV) were optimized. Then, the long-term stability performance was evaluated over the selected catalyst in contrast with Cu/SiO2.

Accurate electron affinity of lanthanum atom

SynopsisAtomic lanthanum anion La− is the best candidate for laser cooling of any atomic anions by far. The previous theoretical studies showed that La− has very a complicated electronic structure, which cannot be well resolved by the traditional photoelectron spectroscopy. In the present work, we used the slow-electron velocity-map imaging method in combination with an ion trap to measure the electronic structure of La−. The electron affinity of La is accurately determined to be 4496.97(20) cm−1 or 0.557553(25) eV.

Electron Confinement and Magnetism of (LaTiO3)1/(SrTiO3)5 Heterostructure: A Diffusion Quantum Monte Carlo Study.

We have applied the diffusion quantum Monte Carlo (DMC) method to study the electron confinement and magnetic structure in the (LaTiO3)1/(SrTiO3)5 heterostructure. The DMC results were compared with various density functional theory (DFT) methods, including local density approximation (LDA), generalized gradient approximation (GGA), LDA+U, and GGA+U, as well as the recently proposed strongly constrained appropriately normed (SCAN) and van der Waals-Bayesian error estimation functional (vdW-BEEF). We found that many-body correlations are crucial to accurately describe the localization of the two-dimensional (2D) electron gas around the lanthanum planes. DMC predicts 20% more electron density within the first interfacial titanium layer in (LaTiO3)1/(SrTiO3)5 than LDA+U, suggesting that the degree of confinement of the 2D electron gas in the interfacial region is underestimated with semilocal DFT approximations. DMC yields the ferromagnetic (FM) state as the ground state of (LaTiO3)1/(SrTiO3)5 and the antiferromagnetic (AFM) and nonmagnetic (NM) states that are higher in energy by 37(15) and 238(15) meV per lanthanum atom at the interface, respectively. Most DFT methods yield the FM and NM states within less than 25 meV in energy and could not find the AFM state.

La-doped diamond films prepared through microwave plasma chemical vapor deposition

La-doped diamond films were deposited through a microwave plasma chemical vapor deposition (MPCVD) system. The effects of La addition on the morphology, microstructure, and quality of the diamond films were systematically investigated. The analysis of secondary ion mass spectroscopy and X-ray photoelectron spectroscopy indicates that lanthanum atoms were incorporated into the diamond films through MPCVD with lanthanum (III) acetate as a precursor. The characterization results reveal that different lanthanum dopant flows can affect the morphology, the preferred orientation of the crystal, and the diamond phase fraction in the films. Upon the lanthanum addition with the dopant flow of 30 sccm, the intensity ratio of the (220) to (111) peaks [I(220)/I(111)] decreases from 20% to 17% and the sp3/sp2 ratio is reduced from 8.53 to 5.89. However, with the increase of the lanthanum dopant flow to 90 sccm, the intensity ratio of I(220)/I(111) rises up to 39% and the sp3/sp2 ratio increases to 8.99. Therefore, a certain amount of lanthanum addition can promote the growth of (110) orientation grains and enhances the sp3 phase fraction in the deposited diamond films. The results obtained from this study provide a hint for adjusting the morphology and microstructure of diamond films with rare earth element doping.

Measurement of the electron affinity of the lanthanum atom

Atomic lanthanum anion ${\mathrm{La}}^{\ensuremath{-}}$ is the best candidate for laser cooling of any atomic anions found so far. The bound-bound electric dipole transitions of ${\mathrm{La}}^{\ensuremath{-}}$ have been identified and measured. Theoretical studies have shown that ${\mathrm{La}}^{\ensuremath{-}}$ has a very complicated electronic structure, which cannot be well resolved by the traditional photoelectron spectroscopy. In the present work, we report high-resolution photoelectron spectroscopy of ${\mathrm{La}}^{\ensuremath{-}}$ via the slow-electron velocity-map imaging method in combination with an ion trap. The electron affinity of La was determined to be $4496.97(20)\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ or 0.557 553(25) eV. In addition, the energy levels of ${\mathrm{La}}^{\ensuremath{-}}$, $^{3}F_{3}^{e}$, $^{3}F_{4}^{e}$, $^{1}D_{2}^{e}$, $^{1}D_{2}^{o}$, $^{3}P_{0}^{e}$, $^{3}P_{1}^{e}$, and $^{3}P_{2}^{e}$, were also determined.

La3Ni4Al2: a new layered aluminide

Abstract The new ternary compound La3Ni4Al2 has been synthesized and the crystal structure has been studied by X-ray single crystal diffraction. La3Ni4Al2 is the first aluminide, crystallizing in the La3Ni4Ga2-type. The crystal structure of La3Ni4Al2 consists of La-layers and hetero-atomic Ni/Al layers, sequentially alternating along the a axis (pseudo-hexagonal c axis). According to electronic structure calculations using the tight-binding linear muffin-tin orbital method in the atomic-sphere approximation (TB-LMTO-ASA), strong Al–Ni interactions have been established. The coordination polyhedra for the Al atoms are cuboctahedra, whereas the bicapped square prism and bicapped square antiprism are typical for nickel atoms. The lanthanum atoms are enclosed in pseudo Frank–Kasper polyhedra.

Lanthanum Complex with Neridronic Acid: Synthesis and Properties

Currently, various amino bisphosphonates are widely used in the treatment of many bone diseases. One of the most well-known complex compounds of neridronic acid (6-amino-1-hydroxyhexylidene-1,1- bisphosphonic acid) is sodium neridronate – a bisphosphonate, which is used to treat osteogenesis and Paget's disease. However, there is no data on compounds of neridronic acid with rare earth elements. A new complex of lanthanum with 6-amino-1-hydroxyhexylidene-1,1-bisphosphonic acid (I) was obtained and characterized by various physicochemical methods (chemical analysis, IR spectroscopy, solid-phase 31P NMR spectroscopy, optical microscopy, PCA, DTA). According to the research data the complex I has the composition {La[(H3N-(CH2)5-C(OH)(PO2(OH))2]2(H2O)2}[OH]·H2O and represents the coordination 1D-polymer due to two bridged phosphonic groups with lanthanum atoms in a tetragonal-antiprismatic environment. In a crystal, polymer chains form a 3D-frame porous structure by means of strong hydrogen bonds O─H ··· O and N─H ··· O with endless channels, available to include a variety of inorganic anions or small organic molecules. A study under the microscope showed that the sample is needle crystals (thin rods) of different lengths. The particle size distribution was obtained by laser diffraction, and the average particle size was determined: 50 µm in length and 2.5 µm in thickness.

Исследование природных лантансодержащих цеолитов методом растровой электронной микроскопии

Методами растровой электронной микроскопии и энергодисперсионной рентгеновской спектроскопии установлено распределение ионов лантана в структуре природных цеолитов – стильбита, шабазита, анальцима, мезолита. Показано, что ионы лантана по поверхности зерна цеолита локализованы неравномерно, концентрируясь на различных структурных дефектах в составе кристаллической фазы.

Radiative Transition Parameters in Atomic Lanthanum from Pseudo-Relativistic Hartree–Fock and Fully Relativistic Dirac–Hartree–Fock Calculations

Calculated radiative transition probabilities and oscillator strengths are reported for 392 lines of neutral lanthanum (La I) atom in the spectral range from the near ultraviolet to the mid infrared. They were obtained using two different theoretical methods based on the pseudo-relativistic Hartree–Fock (HFR) and the fully relativistic multiconfiguration Dirac–Hartree–Fock (MCDHF) approaches, both including the most important intravalence and core-valence electron correlations. The quality of these radiative parameters was assessed through detailed comparisons between the results obtained using different physical models and between our theoretical results and the experimental data, where available. Of the total number of La I lines listed in the present work, about 60% have gf- and gA-values determined for the first time.

Structure and microstructure characterization of the La2SrB10O19 glass-ceramics

The crystal structure of new lanthanum strontium borate glass-ceramics was refined by the Rietveld method. The results showed that La2SrB10O19 has the monoclinic crystal structure, space group C2 (No. 5) with a = 11.1170(6), b = 6.5667(3), c = 9.2363(3) ?, ? = 91.481?, V = 674.04(7) ?3, two formula units per unit-cell, and density 3.830 g cm?3. The main building units of the crystal structure are BO4 tetrahedra and BO3 triangles. Clusters composed of [B5O12] form an infinite double layer running perpendicular to the c-axis. Lanthanum atoms, situated in [B5O12]n layers, are coordinated with 10 oxygen atom in a form of LaO10 polyhedra, while Sr atoms, located between [B5O12]n layers, are coordinated with 8 oxygen atoms in a form of SrO8 polyhedra. Microstructural measurements contain both crystallite domain sizes and microstrain calculations obtained by the Warren-Averbach and the simplified integral-breadth methods.