Search results for "ground"

Temperature Dependence of Electronic and Magnetic Properties of (DOEO)<sub>4</sub>[HgBr<sub>4</sub>]·TCE Single Crystals

2015

The temperature dependence of electronic and magnetic properties of the organic charge-transfer salt (DOEO)4[HgBr4]·TCE was investigated using magnetometry. The magnetic susceptibility shows a maximum at 40 K followed by an onset of a pronounced increase at 70 K and a constant behavior above 120 K. Implications on the charge carrier density are discussed. Combining the magnetometry with resistivity and ESR measurements we propose a sequence of insulating, metallic and semiconducting behavior with increasing temperature. Our results indicate that (DOEO)4[HgBr4]·TCE is close to the boundary between an insulating and conducting ground state.

C-, N-, S-, and Fe-Doped TiO2 and SrTiO3 Nanotubes for Visible-Light-Driven Photocatalytic Water Splitting: Prediction from First Principles

2015

The ground state electronic structure and the formation energies of both TiO2 and SrTiO3 nanotubes (NTs) containing CO, NO, SO, and FeTi substitutional impurities are studied using first-principles calculations. We observe that N and S dopants in TiO2 NTs lead to an enhancement of their visible-light-driven photocatalytic response, thereby increasing their ability to split H2O molecules. The differences between the highest occupied and lowest unoccupied impurity levels inside the band gap (HOIL and LUIL, respectively) are reduced in these defective nanotubes down to 2.4 and 2.5 eV for N and S doping, respectively. The band gap of an NO+SO codoped titania nanotube is narrowed down to 2.2 eV …

Production of hydrogen negative ions in an ECR volume source: balance between vibrational excitation and ionization

2018

International audience; The operation of an ECR-driven (2.45 GHz) hydrogen negative ion source is studied. Electron densities and temperatures are investigated with electrostatic probes and negative ion densities are measured with laser photodetachment. Vacuum ultraviolet irradiance measurements are focused on molecular transitions to the ground state while high-resolution visible emission spectroscopy is used to study the transitions between excited states for both molecules and atoms. The standalone operation of the source is found to be more efficient in higher pressures (12 mTorr) where negative ion densities are as high as 4×109 cm−3. Further investigation on the operation of the sou…

Revealing the correlation between real-space structure and chiral magnetic order at the atomic scale

2017

We image simultaneously the geometric, the electronic, and the magnetic structures of a buckled iron bilayer film that exhibits chiral magnetic order. We achieve this by combining spin-polarized scanning tunneling microscopy and magnetic exchange force microscopy (SPEX) to independently characterize the geometric as well as the electronic and magnetic structures of nonflat surfaces. This new SPEX imaging technique reveals the geometric height corrugation of the reconstruction lines resulting from strong strain relaxation in the bilayer, enabling the decomposition of the real-space from the electronic structure at the atomic level and the correlation with the resultant spin-spiral ground sta…

A Novel Polyoxotungstate Containing atriangulo Ni3II Cluster with Ferromagnetic Exchange Interactions and anS= 3 Ground State

1992

Hydrogen in metals: Quantum aspects

1984

Hydrogen atoms are usually considered chemisorbed at well-defined sites on surfaces. We advocate a completelydifferent view, and demonstrate that chemisorbed hydrogen exhibits pronounced quantum effects. The hydrogen atom is to a large degree delocalized in both ground and excited-stated configurations: a proper description can only be given in terms of hydrogen energy bands. An analogous picture emerges for hydrogen isotopes (including muon) diffusing interstitially in bulk metals. The ground state there corresponds to a self-trapped situation: a localized impurity with an associated lattice distortion field. A powerful computational scheme is presented, which entails (i) the construction …

Alkali-Activated Adsorbents from Slags: Column Adsorption and Regeneration Study for Nickel(II) Removal

2021

Alkali-activated adsorbents were synthesized by mixing three different slags from the steel industry: blast furnace slag (BFS), ladle slag (LS), and Lintz–Donawitz converter slag (LD). These powdered slag-based geopolymers (GP) were used to remove nickel(II) from aqueous solutions in fixed-bed column studies. The experiments were conducted in pH 6 using a phosphate buffer with initial nickel(II) concentration of 50 mg/L. Samples were taken at time intervals of between 5 and 90 min. Three adsorption–desorption cycles were implemented with a flow rate of 5 mL/min. The geopolymers were characterized by Fourier-Transform Infrared Spectroscopy (FTIR), X-ray powder diffraction (XRD), Field Emissi…

First principles calculations on CeO2 doped with Tb3+ ions

2019

This research was funded by the Latvian Council of Science (under the grant project lzp-2018/1-0147). Authors thank W. Chueh, J. Serra, R. Merkle, A. Popov for fruitful discussions.

Differences and Similarities between the Isotypic AntimonidesMFe1−xSb, ScCo1−xSb, andMNiSb (M=Zr, Hf)

1999

The new antimonides MFe{sub 1{minus}x}Sb can be synthesized by arc-melting of M, Fe, and MSb{sub 2} (M = Zr, Hf). All title compounds crystallize in the TiNiSi structure type (space group Pnma, Z = 4). The lattice parameters of the new phases of MFe{sub 1{minus}x}Sb, as obtained from the bulk samples of the nominal compositions MFeSb, are a = 681.4(1) pm, b = 417.87(7) pm, c = 740.3(1) pm for ZrFe{sub 1{minus}x}Sb and a = 674.0(1) pm, b = 412.0(2) pm, c = 729.7(2) pm for HfFe{sub 1{minus}x}Sb. Under the reaction conditions used, the occupancy factors of the iron position content of ZrFe{sub 1{minus}x}Sb does not exceed 68(1)% (i.e., x = 0.32(1)). Extended Hueckel calculations, performed on …

Detection of deuterium retention by LIBS at different background pressures

2017

ITER plans foresee the quantitative diagnostics of fuel retention in reactor walls at near-atmospheric pressures. Using laser induced breakdown spectroscopy (LIBS) for this purpose assumes a reliable resolving of Balmer α-lines of hydrogen isotopes in spectra of plasma produced by focused laser radiation onto the target surface. To develop LIBS for quantitative diagnostics of fuel retention during the maintenance breaks of ITER, the effect of background gas pressure on the laser-induced plasma characteristics has been studied. The background pressure limits the expansion rate of plasma and as a result it leads to higher plasma concentrations. At the same time the limiting factor of the reso…