75 research outputs found
Ab Initio Predictions of Spin Defects in Simple Oxides
Simple oxides hold promises as hosts of spin qubits with coherence times tens
of times longer than those measured in diamond and silicon carbide. However, no
suitable spin defect has yet been found in these systems. Using high-throughput
first principles calculations, we predict spin defects in calcium oxide with
electronic properties remarkably similar to those of the NV-center in diamond.
These defects are charged complexes where a dopant atom -- Sb, Bi or I --
occupies the volume vacated by adjacent cation and anion vacancies. We show
that the Bi complex emits in the telecommunication range and the computed
many-body energy levels indicate that an optical cycle required for qubit
initialization can be realized. Our results pave the way to designing quantum
states with long coherence times in simple oxides, which are attractive
materials for quantum technologies
Rashba and Dresselhaus effects in 2D Pb-I-based perovskites
Bulk hybride halide perovskites are governed by significant Rashba and
Dresselhaus splitting. This indicates that such effects will not only affect
their optoelectronic properties but also those of their two dimensional layered
relatives. This work aims at understanding how different ways of symmetry
breaking influence these effects in those materials. For this purpose, model
structures are adopted where the organic compounds are replaced by Cs atoms.
Disregarding possible distortions in the inorganic layers, results in
structures with composition CsPbI. Using the all-electron
full-potential density-functional-theory code \texttt{exciting}, the impact of
atomic displacement on the band structure is systematically studied for ,
2, 3 and . The displacement patterns that yield Rashba or Dresselhaus
splitting are identified, and the amount of the splitting is determined as a
function of displacement. Furthermore, the spin textures in the electronic
states around the band gap are analyzed to differentiate between Rashba and
Dresselhaus effects. This study reveals in-plane Pb displacements as the origin
of the strongest effects.Comment: 10 pages, 8 figures, 1 tabl
The prevalence rates of refractive errors among children, adolescents, and adults in Germany
Sandra Jobke1, Erich Kasten2, Christian Vorwerk31Institute of Medical Psychology, 3Department of Ophthalmology, Otto-von Guericke-University of Magdeburg, Magdeburg, Germany; 2Institute of Medical Psychology, University Hospital Schleswig-Holstein, Luebeck, GermanyPurpose: The prevalence rates of myopia vary between 5% in Australian Aborigines to 84% in Hong Kong and Taiwan, 30% in Norwegian adults, and 49.5% in Swedish schoolchildren. The aim of this study was to determine the prevalence of refractive errors in German children, adolescents, and adults.Methods: The parents (aged 24–65 years) and their children (516 subjects aged 2–35 years) were asked to fill out a questionnaire about their refractive error and spectacle use. Emmetropia was defined as refractive status between +0.25D and –0.25D. Myopia was characterized as ≤−0.5D and hyperopia as ≥+0.5D. All information concerning refractive error were controlled by asking their opticians.Results: The prevalence rates of myopia differed significantly between all investigated age groups: it was 0% in children aged 2–6 years, 5.5% in children aged 7–11 years, 21.0% in adolescents (aged 12–17 years) and 41.3% in adults aged 18–35 years (Pearson’s Chi-square, p = 0.000). Furthermore, 9.8% of children aged 2–6 years were hyperopic, 6.4% of children aged 7–11 years, 3.7% of adolescents, and 2.9% of adults (p = 0.380). The prevalence of myopia in females (23.6%) was significantly higher than in males (14.6%, p = 0.018). The difference between the self-reported and the refractive error reported by their opticians was very small and was not significant (p = 0.850).Conclusion: In Germany, the prevalence of myopia seems to be somewhat lower than in Asia and Europe. There are few comparable studies concerning the prevalence rates of hyperopia.Keywords: Germany, hyperopia, incidence, myopia, prevalenc
Excitation Pathways in Resonant Inelastic X-Ray Scattering of Solids
We present a novel derivation of resonant inelastic x-ray scattering (RIXS)
which yields an expression for the RIXS cross section in terms of emission
pathways between intermediate and final many-body states. Thereby electron-hole
interactions are accounted for, as obtained from full diagonalization of the
Bethe-Salpeter equation within an all-electron first-principles framework. We
demonstrate our approach with the emission spectra of the fluorine K edge in
LiF, and provide an in-depth analysis of the pathways that determine the
spectral shape. Excitoninc effects are shown to play a crucial role in both the
valence and core regime
Integrated Planning of Multi-energy Grids: Concepts and Challenges
In order to meet ever-stricter climate targets and achieve the eventual
decarbonization of the energy supply of German industrial metropolises, the
focus is on gradually phasing out nuclear power, then coal and gas combined
with the increased use of renewable energy sources and employing hydrogen as a
clean energy carrier. While complete electrification of the energy supply of
households and the transportation sector may be the ultimate goal, a
transitional phase is necessary as such massive as well as rapid expansion of
the electrical distribution grid is infeasible. Additionally, German industries
have expressed their plans to use hydrogen as their primary strategy in meeting
carbon targets. This poses challenges to the existing electrical, gas, and
heating distribution grids. It becomes necessary to integrate the planning and
developing procedures for these grids to maximize efficiencies and guarantee
security of supply during the transition. The aim of this paper is thus to
highlight those challenges and present novel concepts for the integrated
planning of the three grids as one multi-energy grid.Comment: NEIS 2022; Conference on Sustainable Energy Supply and Energy Storage
System
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