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We present a formalism for the resonant inelastic x-ray scattering (RIXS) cross section. The resulting compact expression in terms of polarizability matrix elements, particularly lends itself to the implementation in an all-electron many-body perturbation theory (MBPT) framework, which is realized in the full-potential package exciting. With the carbon K edge RIXS of diamond and the oxygen K edge RIXS of $\beta-\mathrm{Ga_2 O_3}$, respectively, we demonstrate the importance of electron-hole correlation and atomic coherence in the RIXS spectra.

We present a Green's function formulation of the quantum defect embedding theory (QDET) where a double counting scheme is rigorously derived within the $G_0 W_0$ approximation. We then show the robustness of our methodology by applying the theory with the newly derived scheme to several defects in diamond. Additionally, we discuss a strategy to obtain converged results as a function of the size and composition of the active space. Our results show that QDET is a promising approach to investigate strongly correlated states of defects in solids.

Single-shot readout of divacancy spin qubits in silicon carbide is demonstrated through spin-selective two-photon ionization and subsequent optical charge readout. With this readout, we measure single-spin coherence times of over five seconds.

We demonstrate single-shot readout of spin qubits in silicon carbide through spin-selective two-photon ionization and subsequent optical charge readout. We use this readout to measure single-spin electronic coherence times of over five seconds.

Here we report the optical and x-ray absorption (XAS) spectra of the wide-band-gap oxide MgO using density functional theory (DFT) and many-body perturbation theory (MBPT). Our comprehensive study of the electronic structure shows that while the band gap is underestimated with the exchange-correlation functional PBEsol (4.58 eV) and the hybrid functional HSE06 (6.58 eV) compared to the experimental value (7.7 eV), it is significantly improved (7.52 eV) and even overcompensated (8.53 eV) when quasiparticle corrections are considered. Inclusion of excitonic effects by solving the Bethe-Salpeter equation (BSE) yields the optical spectrum in excellent agreement with experiment. Excellent agreement is observed also for the O and Mg K-edge absorption spectra, demonstrating the importance of the electron-hole interaction within MBPT. Projection of the electron-hole coupling coefficients from the BSE eigenvectors on the band structure allows us to determine the origin of prominent peaks and identify the orbital character of the relevant contributions. The real space projection of the lowest energy exciton wavefunction of the optical spectrum indicates a Wannier-Mott type, whereas the first exciton in the O K-edge is more localized.

Quantum computers hold promise to improve the efficiency of quantum simulations of materials and to enable the investigation of systems and properties more complex than tractable at present on classical architectures. Here, we discuss computational frameworks to carry out electronic structure calculations of solids on noisy intermediate scale quantum computers using embedding theories, and we give examples for a specific class of materials, i.e., spin defects in solids. These are promising systems to build future quantum technologies, e.g., computers, sensors and devices for quantum communications. Although quantum simulations on quantum architectures are in their infancy, promising results for realistic systems appear to be within reach.

The search for new wide band gap materials is intensifying to satisfy the need for more advanced and energy efficient power electronic devices. Ga$_2$O$_3$ has emerged as an alternative to SiC and GaN, sparking a renewed interest in its fundamental properties beyond the main $\beta$-phase. Here, three polymorphs of Ga$_2$O$_3$, $\alpha$, $\beta$ and $\varepsilon$, are investigated using X-ray diffraction, X-ray photoelectron and absorption spectroscopy, and ab initio theoretical approaches to gain insights into their structure - electronic structure relationships. Valence and conduction electronic structure as well as semi-core and core states are probed, providing a complete picture of the influence of local coordination environments on the electronic structure. State-of-the-art electronic structure theory, including all-electron density functional theory and many-body perturbation theory, provide detailed understanding of the spectroscopic results. The calculated spectra provide very accurate descriptions of all experimental spectra and additionally illuminate the origin of observed spectral features. This work provides a strong basis for the exploration of the Ga$_2$O$_3$ polymorphs as materials at the heart of future electronic device generations., Comment: Updated manuscript version after peer review

We present a method to construct an efficient approximation to the bare exchange and screened direct interaction kernels of the Bethe-Salpeter Hamiltonian for periodic solid state systems via the interpolative separable density fitting technique. We show that the cost of constructing the approximate Bethe-Salpeter Hamiltonian scales nearly optimally as $\mathcal{O}(N_k)$ with respect to the number of samples in the Brillouin zone $N_k$. In addition, we show that the cost for applying the Bethe-Salpeter Hamiltonian to a vector scales as $\mathcal{O}(N_k \log N_k)$. Therefore the optical absorption spectrum, as well as selected excitation energies can be efficiently computed via iterative methods such as the Lanczos method. This is a significant reduction from the $\mathcal{O}(N_k^2)$ and $\mathcal{O}(N_k^3)$ scaling associated with a brute force approach for constructing the Hamiltonian and diagonalizing the Hamiltonian respectively. We demonstrate the efficiency and accuracy of this approach with both one-dimensional model problems and three-dimensional real materials (graphene and diamond). For the diamond system with $N_k=2197$, it takes $6$ hours to assemble the Bethe-Salpeter Hamiltonian and $4$ hours to fully diagonalize the Hamiltonian using $169$ cores when the brute force approach is used. The new method takes less than $3$ minutes to set up the Hamiltonian and $24$ minutes to compute the absorption spectrum on a single core.

We present a high-performance solver for dense skew-symmetric matrix eigenvalue problems. Our work is motivated by applications in computational quantum physics, where one solution approach to solve the Bethe-Salpeter equation involves the solution of a large, dense, skew-symmetric eigenvalue problem. The computed eigenpairs can be used to compute the optical absorption spectrum of molecules and crystalline systems. One state-of-the art high-performance solver package for symmetric matrices is the ELPA (Eigenvalue SoLvers for Petascale Applications) library. We exploit a link between tridiagonal skew-symmetric and symmetric matrices in order to extend the methods available in ELPA to skew-symmetric matrices. This way, the presented solution method can benefit from the optimizations available in ELPA that make it a well-established, efficient and scalable library. The solution strategy is to reduce a matrix to tridiagonal form, solve the tridiagonal eigenvalue problem and perform a back-transformation for eigenvectors of interest. ELPA employs a one-step or a two-step approach for the tridiagonalization of symmetric matrices. We adapt these to suit the skew-symmetric case. The two-step approach is generally faster as memory locality is exploited better. If all eigenvectors are required, the performance improvement is counteracted by the additional back transformation step. We exploit the symmetry in the spectrum of skew-symmetric matrices, such that only half of the eigenpairs need to be computed, making the two-step approach the favorable method. We compare performance and scalability of our method to the only available high-performance approach for skew-symmetric matrices, an indirect route involving complex arithmetic. In total, we achieve a performance that is up to 3.67 times higher than the reference method using Intel’s ScaLAPACK implementation. Our method is freely available in the current release of the ELPA library.

Theoretical spectroscopy is a powerful tool to describe and predict optical properties of materials. While nowadays routinely performed, first-principles calculations only provide bulk dielectric tensors in Cartesian coordinates . These outputs are hardly comparable with experimental data, which are typically given by macroscopic quantities , crucially depending on the laboratory setup. Even more serious discrepancies can arise for anisotropic materials, e.g., organic crystals, where off-diagonal elements of the dielectric tensor can significantly contribute to the spectral features . Here, we present LayerOptics , a versatile and user-friendly implementation, based on the solution of the Maxwell’s equations for anisotropic materials, to compute optical coefficients in anisotropic layered materials. We apply this tool for post-processing full dielectric tensors of molecular materials, including excitonic effects, as computed from many-body perturbation theory using the exciting code. For prototypical examples, ranging from optical to X-ray frequencies, we show the importance of combining accurate ab initio methods to obtain dielectric tensors, with the solution of the Maxwell’s equations to compute optical coefficients accounting for optical anisotropy of layered systems. Good agreement with experimental data supports the potential of our approach, in view of achieving microscopic understanding of spectroscopic properties in complex materials.

In a combined theoretical and experimental work, we investigate X-ray Absorption Near-Edge Structure (XANES) spectroscopy of the I $L_3$ and the Pb $M_5$ edges of the methylammonium lead iodide ($\textrm{MAPbI}_3$) hybrid inorganic-organic perovskite and its binary phase $\textrm{PbI}_2$. The absorption onsets are dominated by bound excitons with sizable binding energies of a few hundred meV and pronounced anisotropy. The spectra of both materials exhibit remarkable similarities, suggesting that the fingerprints of core excitations in $\textrm{MAPbI}_3$ are essentially given by its inorganic component, with negligible influence from the organic groups. The theoretical analysis complementing experimental observations provides the conceptual insights required for a full characterization of this complex material.

The permeability transition pore (PTP) of inner mitochondrial membranes is a large conductance pathway for ions up to 1500 Da which opening is responsible for ion equilibration and loss of membrane potential in apoptosis and thus in several neurodegenerative diseases. The PTP can be regulated by the Ca2+-activated mitochondrial K channel (BK). Calpains are Ca2+-activated cystein proteases; calpeptin is an inhibitor of calpains. We wondered whether calpain or calpeptin can modulate activity of PTP or BK. Patch clamp experiments were performed on mitoplasts of rat liver (PTP) and of an astrocytoma cell line (BK). Channel-independent open probability (P o) was determined (PTP) and, taking into account the number of open levels, NPo by single channel analysis (BK). We find that PTP in the presence of Ca2+ (200 μM) is uninfluenced by calpain (13 nM) and shows insignificant decrease by the calpain inhibitor calpeptin (1 μM). The NPo of the BK is insensitive to calpain (54 nM), too. However, it is significantly and reversibly inhibited by the calpain inhibitor calpeptin (IC50 = 42 μM). The results agree with calpeptin-induced activation of the PTP via inhibition of the BK. Screening experiments with respirometry show calpeptin effects, fitting to inhibition of the BK by calpeptin, and strong inhibition of state 3 respiration.

We present an ab initio study of core excitations of solid-state materials focussing on the role of electron-hole correlation. In the framework of an all-electron implementation of many-body perturbation theory into the exciting code, we investigate three different absorption edges of three materials, spanning a broad energy window, with transition energies between a few hundred to thousands of eV. Specifically, we consider excitations from the Ti $K$ edge in rutile and anatase $\textrm{TiO}_2$, from the Pb $M_4$ edge in $\textrm{PbI}_2$, and from the Ca $L_{2,3}$ edge in $\textrm{CaO}$. We show that the electron-hole attraction rules x-ray absorption for deep core states, when local fields play a minor role. On the other hand, the local-field effects introduced by the exchange interaction between the excited electron and the hole dominate excitation processes from shallower core levels, separated by a spin-orbit splitting of a few eV. Our approach yields absorption spectra in good agreement with available experimental data, and allows for an in-depth analysis of the results, revealing the electronic contributions to the excitations, as well as their spatial distribution., Comment: https://journals.aps.org/prb/accepted/51079O49M371532007297d377db6917b215a22721

Purpose: The normal human cornea is devoid of both blood and lymphatic vessels and actively maintains this avascularity (corneal angiogenic privilege). Whether and when corneal angiogenic privilege is achieved during development is unknown. Methods: This study analyzed whether the cornea is primarily devoid of both blood and lymphatic vessels during intrauterine development or whether secondary regression of pre-existing vessels occurs before delivery. Indirect double immunohistochemistry was performed on 4-μm serial pupil-optic disc sections of paraffin-embedded human eyes stillborn at gestational ages of 17 to 41 weeks with antibodies against von Willebrand factor (vWF; factor VIII-associated antigen) as a panendothelial marker and with antibodies against lymphatic vessel endothelial hyaluronate receptor 1 (LYVE1) as a marker specific for lymphatic vascular endothelium. Results: Human corneas were devoid of both vWF +++ /LYVE-1 - blood vessels and vWF + /LYVE-1 +++ lymphatic vessels at all time-points analyzed. In contrast, there were numerous blood and lymphatic vessels detectable in the adjacent conjunctiva. Conclusion: The normal human cornea is primarily avascular and devoid of both blood and lymphatic vessels. Corneal angiogenic privilege is already achieved very early during fetal intrauterine development. This suggests early and strong expression of both antiangiogenic and antilymphangiogenic factors in the human cornea during development.

Calculations are presented of the electronic structure and X-ray spectra of materials with correlatedd- andf-electron states based on the Hubbard model, a real-space multiple-scattering formalism and a rotationally invariant local density approximation. Values of the Hubbard parameter are calculatedab initiousing the constrained random-phase approximation. The combination of the real-space Green's function with Hubbard model corrections provides an efficient approach to describe localized correlated electron states in these systems, and their effect on core-level X-ray spectra. Results are presented for the projected density of states and X-ray absorption spectra for transition metal- and lanthanide-oxides. Results are found to be in good agreement with experiment.

Logistics Journal: Proceedings, Vol. 06, Iss. 01 - Im Rahmen eines seitens der AiF geforderten Forschungsvorhabens wurde zur weiteren Steigerung der Leistungsfahigkeit von Schwerlast-Regalbediengeraten das dynamische Verhalten dieser Systeme analysiert. Dazu wurde eine umfangreiche experimentelle Schwingungsanalyse an einem bestehen-den Regalbediengerat durchgefuhrt. Anschliesend wurde ein Ersatzmodell als Mehrkorpersimulations-Modell von diesem System erstellt und damit Untersuchungen zur dynamischen Beurteilung durchgefuhrt, in dem beispielsweise die Last, Hubhohe und Geschwindigkeit erhoht wurden.

Logistics Journal: Proceedings, Vol. 06, Iss. 01 - Im Lagerbereich von intralogistischen Systemen werden zur Handhabung von Waren unterschiedliche technische Komponenten eingesetzt, wie z.B. Horizontalkommissionierer, elektrische Gabelhubwagen oder Fahrerlose Transportsysteme. Es gibt jedoch noch zahlreiche Aufgaben bei denen eine neue kompaktere und flexiblere Transporttechnik die Arbeit deutlich erleichtern wurde, so z.B. beim Rangieren auf LKW-Ladebordwanden und in beengten Lager- oder Kaufhausbereichen. Es wurde eine neuartige Transportvorrichtung entwickelt, bei der sowohl die Fahr-, Lenk- und Hubfunktionen als auch die benotigte Energieversorgungs- und Steuerungstechnik implementiert sind. Die Transportvorrichtung besitzt dabei ungefahr die Abmessungen einer Gabel eines Gabelhubwagens.

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, prevalence

GIMS (Graphical Interface for Materials Simulations) is an open-source browser-based tool- box for electronic-structure codes. It supports the generation of input files for first-principles electronic-structure calculations and workflows, as well as the automated analysis and visual- ization of the results. GIMS is deliberately extendable to enable support for any electronic- structure code. Presently, it supports two different software packages: the numerical atom centered orbital package FHI-aims and the LAPW code exciting.