3d States Research Articles

Mechanism-Based damage and failure of Fused Filament Fabrication components

Fused Filament Fabrication (FFF) is a polymer-based Additive Manufacturing (AM) technology that produces complex layered components. The characterization of the inherited orthotropic properties of FFF components and their failure analysis is a challenging endeavor. In this paper, the failure mechanics of FFF parts are studied via a Mechanism-Based (MB) damage material model. A MB damage criterion is developed by considering that the damage is driven by different failure modes identified according to the printing pattern. The developed criterion is compared to the Tsai–Wu (TW) criterion, which is commonly used for orthotropic materials with different strengths in tension and compression. Also, a MB cracking model that incorporates the orthotropic brittleness of FFF components is developed. The application of this cracking model requires solely two parameters to be defined.Numerical predictions of the cracking of two different experimental tests illustrate the similarities and the differences between the MB and TW damage criteria. The results demonstrate that the MB damage criterion can accurately match the experimental results, while the TW criterion fails to describe correctly the failure modes in complex 3D stress states.

Impact of the states in the electronic structure of the intermediate-valence superconductor CeIr3

The electronic structure of the f-based superconductor was studied by photoelectron spectroscopy. The energy distribution of the states were revealed by the resonant photoelectron spectroscopy. The states were mostly distributed in the vicinity of the Fermi energy, suggesting the itinerant character of the states. The contribution of the states to the density of states (DOS) at the Fermi energy was estimated to be nearly half of that of the states, implying that the states have a considerable contribution to the DOS at the Fermi energy. The core-level and x-ray absorption spectra were analyzed based on a single-impurity Anderson model. The number of the states in the ground state was estimated to be , which is much larger than the values obtained in the previous studies (i.e. ).

Latest Advances in Perovskite LED Research

In recent years, there is a growing need for a better performance, lower cost, brighter and longer life luminous and display technology. Perovskite materials have attracted widespread attention because of their excellent performance in optoelectronic devices. For example, it has high carrier mobility, small emission line width, bandgap tunability, and strong photoluminescence quantum yield (PLQY). As a result, perovskite light-emitting diodes (LEDs) have developed rapidly over the past few years. This article starts with the basic parameters of perovskite LED (PeLED) devices and describes the basic structure and working principle of perovskite LED devices. And it mainly reviews the development history of 3D perovskite LEDs and states the latest progress in the research of perovskite quantum dots (QDs) and hole transport layers (HTLs) and electron transport layers (ETLs) in perovskite LED devices. Finally, the problems restricting the development of perovskite LEDs are summarized. This article offers a comprehensive understanding of perovskite LED devices and their future research directions.

Electronic and optical properties of Sc2C(OH)2 with phenylsulfonic groups: A first-principles study

Polystyrene sulfonic acid (PSS) polymer thin film can be applied to the surface passivation of Si-based semiconductor devices because of its low cost and the ability to be fabricated without the need for extreme temperatures or high vacuum. Here, the phenylsulfonic groups (–pSO3H, a typical part of PSS) were grafted onto the Sc2C(OH)2 the surface to form Sc2C(OH)2–pSO3H. The electronic structure and optical properties were investigated by first-principles calculations. The results show that Sc2C(OH)2–pSO3H is a direct bandgap semiconductor material with a bandgap of 0.99 eV, which is higher than that of Sc2C(OH)2. The bandgap of Sc2C(OH)2–pSO3H has a small change by replacing cation H of –pSO3H with Li, Na and K, indicating that the Sc2C(OH)2–pSO3H maintains its semiconductor properties. The reason is that the conduction band minimum (CBM) state and the valence band maximum (VBM) are mainly determined by the contribution of C 2p states and Sc 3d states of the main body Sc2C(OH)2. Versus the conventional photovoltaic material Si, the absorption coefficient of Sc2C(OH)2–pSO3H is very high, thus resulting in a maximum photoelectric conversion efficiency of up to 31 %. These results suggest promising 2D visible light absorption materials that are photovoltaics in solar cells.

Machine learning-derived reaction statistics for 3D spectroimaging of copper sulfidation in heterogeneous rubber/brass composites

The sulfidation of copper derived from copper-zinc alloy (brass) in sulfur-containing rubber, used for plating steel-cord-reinforced rubber tires, is suggested to be the key reaction for the adhesive behavior between brass and rubber in tires. However, the heterogeneous structures of rubber/brass interfaces have prevented us from understanding the sulfidation of metallic copper in brass and the formation of copper sulfides at the brass surface and buried rubber interface. Here, we visualize the 3D spatial location and chemical states of copper species in a rubber/brass composite during its aging process by 3D X-ray spectroimaging with X-ray absorption fine structure-computed tomography. Machine learning-derived reaction statistics of the 3D spectroimaging data reveal the reaction mechanism of copper sulfidation in the heterogeneous rubber/brass composite.

First-principles study of luminescence and electronic properties of Ce-doped Y2SiO5.

The transition of energy from the 4f to the 5d state is a fundamental element driving various applications, such as phosphors and optoelectronic devices. The positioning of the 4f ground states and the 5d excited states significantly influences this energy shift. In our research, we delve into the placement of these states utilizing a hybrid density functional theory (DFT) combined with spin-orbit coupling (SOC) via the supercell method. Additionally, we scrutinize the transition energy, applying the constrained density functional theory (cDFT) approach in conjunction with the ΔSCF method. Our study illustrates that the synergy of cDFT and SOC generates a discrepancy of about 2% for Ce1 and 4% for Ce2 when comparing the calculated results to experimental data. Moreover, We have determined the positions of the 4f ground states to be 2.73eV above the Valence Band Maximum (VBM) for Ce1 and 2.70eV for Ce2. We also note a tight correlation between the 5d levels identified in the experimental data and the theoretical outcomes derived from wave function calculations at the CASPT2 accuracy level.

Efficient Removal of Antibiotic Resistance Genes through 4f‐2p‐3d Gradient Orbital Coupling Mediated Fenton‐Like Redox Processes

AbstractPeroxymonosulfate (PMS) mediated radical and nonradical active substances can synergistically achieve the efficient elimination of antibiotic resistance genes (ARGs). However, enhancing interface electron cycling and optimizing the coupling of the oxygen‐containing intermediates to improve PMS activation kinetics remains a major challenge. Here, Co doped CeVO4 catalyst (Co−CVO) with asymmetric sites was constructed based on Ce 4f−O 2p−Co 3d gradient orbital coupling. The catalyst achieved approximately 2.51×105 copies/mL of extracellular ARGs (eARGs) removal within 15 minutes, exhibited ultrahigh degradation rate (k=1.24 min−1). The effective gradient 4f‐2p‐3d orbital coupling precisely regulates the electron distribution of Ce−O−Co active center microenvironment, while optimizing the electronic structure of Co 3d states (especially the occupancy of eg), promoting the adsorption of oxygen‐containing intermediates. The generated radical and nonradical generated by interfacial electron cycling enhanced by the reduction reaction of PMS at the Ce site and the oxidation reaction at the Co site achieved a significant mineralization rate of ARGs (83.4 %). The efficient removal of ARGs by a continuous flow reactor for 10 hours significantly reduces the ecological risk of ARGs in actual wastewater treatment.

Efficient Removal of Antibiotic Resistance Genes through 4f-2p-3d Gradient Orbital Coupling Mediated Fenton-Like Redox Processes.

Peroxymonosulfate (PMS) mediated radical and nonradical active substances can synergistically achieve the efficient elimination of antibiotic resistance genes (ARGs). However, enhancing interface electron cycling and optimizing the coupling of the oxygen-containing intermediates to improve PMS activation kinetics remains a major challenge. Here, Co doped CeVO4 catalyst (Co-CVO) with asymmetric sites was constructed based on Ce 4f-O 2p-Co 3d gradient orbital coupling. The catalyst achieved approximately 2.51×105 copies/mL of extracellular ARGs (eARGs) removal within 15 minutes, exhibited ultrahigh degradation rate (k = 1.24 min-1). The effective gradient 4f-2p-3d orbital coupling precisely regulates the electron distribution of Ce-O-Co active center microenvironment, while optimizing the electronic structure of Co 3d states (especially the occupancy of eg), promoting the adsorption of oxygen-containing intermediates. The generated radical and nonradical generated by interfacial electron cycling enhanced by the reduction reaction of PMS at the Ce site and the oxidation reaction at the Co site achieved a significant mineralization rate of ARGs (83.4%). The efficient removal of ARGs by a continuous flow reactor for 10 hours significantly reduces the ecological risk of ARGs in actual wastewater treatment.

The Excitation of the 3D and 4D States of Atomic Hydrogen by Electron Impact

The excitation cross-sections of the 3D and 4D states of atomic hydrogen at low incident energies (from 0.90 to 5.00 Ry) were calculated using the variational polarized orbital method, which is also called the hybrid theory. Up to 12 partial waves (L = 2 to 13) were used to obtain converged cross-sections at high energies. The importance of the long-range forces near the threshold region and the behavior of the cross-sections in that region are indicated. The S, P, and D cross-sections are needed if the total excitation cross-sections are measured in addition to the elastic cross-sections. These cross-sections are also useful if the cascade from the D to the P to the S states is considered in the diagnostics of solar and astrophysical observations.

A first-principles study on Ga stabilized δ-Pu phase stability based on structural and electronic properties

The high temperature face-centered-cubic delta phase of plutonium (FCC δ-Pu) is metallurgically important in industrial applications and can be stabilized at room temperature by alloying with small amounts of gallium (Ga). Therefore, it is of fundamental interest to elucidate the factors that govern the δ-Pu-Ga interactions via the electronic structure to understand the stabilization mechanism of the FCC phase. We employed density functional theory to systematically model the change in the structural and electronic properties with increasing Ga concentrations of δ-Pu-Ga alloys. The results indicate that structural optimizations with an applied cubic symmetry constraint are sufficient to describe the alloy properties. The variations in Pu-Pu and Pu-Ga bond lengths and the lattice disorder induced by the Ga substitution at Pu sites are in qualitative agreement with previously published experimental EXAFS data. Additionally, in accordance with the experimental results, the atomic volume decreases as the Ga concentration increases. The alloyformation energydecreasesas the Ga concentrationincreases, indicating an increase in stability and an exothermic alloying reaction. The Pu-Ga electronic interaction is governed principally by hybridization between the Pu 6d and Ga 4p states, with decreasing Pu 5f states at the Fermi energy with increasing Ga content due to the increase of Ga-Pu-Ga bonds within the lattice.

The photocatalytic performance study of La doping AgNbO3 by electronic structure and the carrier lifetime

AgNbO3 semiconductor have attracted much attention due to its unique visible-light photosensitivity. The first-principles calculations were used to investigate the relationship among the structural evolution, electronic structure, optical properties and carrier lifetime of La doped Ag1-xLaxNbO3. The addition of La enlarges the cell volume and inhibits the lattice distortion, which promotes the separation of photogenerated electron-hole pairs. After La doping, the La 4d state gradually extends to the fermi level, resulting in more electrons to participate in the reduction reaction. The light absorption of Ag1-xLaxNbO3 at visible range and the utilization capacity of sunlight are enhanced. The me* of Ag1-xLaxNbO3 is reduced, which is conducive to the charge transfer and guarantees the electronic mobility and carrier lifetime in the compound. Our study demonstrats that La doping can effectively improve the photocatalytic performance of AgNbO3, which provides a reference for the experimental research of photocatalytic water decomposition.

Stress‐Induced Multi‐Stimulus‐Responsive Mechanoluminescence in Mn2+ Doped Double Perovskite Compound

AbstractMulti‐mode mechanoluminescence (ML) materials are have applications such as anti‐counterfeiting, stress sensing, and information security. There is limited general consensuses on the luminescent mechanisms, even though exploring ML mechanism based on defects has shown significance in further studies exploring both ML materials design and application. Here, a deep‐red to near‐infrared (NIR) ML material is reported in a Mn2+‐activated double perovskite‐type compound (CaZnGe2O6: Mn2+). The abundant lattice sites within the crystal structure have enabled Mn2+ doping and defects. Two different photoluminescence (PL) emission bands peaked at 536 and 676 nm from 4T1(4G)→6A1(6S) are observed, which are attributed to the substitution of Zn2+ and Ca2+ sites by Mn2+, respectively. Hence, tunable emissions from green to red are realized in single Mn2+ doping, which can be further regulated by varying the Mn2+ concentration. Electrons and holes are captured by cation and anion defects ( and , , vacancy of Zn, Ca and O ions), followed by the combination of such carriers to transfer energy to the Mn2+ 3d states to produce ML/persistent luminescence (PersL) under mechanical/thermal stimuli. Proof‐of‐concept applications in multi‐mode anti‐counterfeiting, temperature sensing, and X‐ray imaging fields are demonstrated. These results will deepen the understanding of single Mn2+‐doped multi‐stimulus‐responsive ML materials, inspiring the development of more high‐performance ML phosphors for practical applications.

Can [formula omitted] excitations mediate pairing?

The Cu-3d states in the high-Tc cuprates are often described as a single band of 3dx2−y2 states, with the other four 3d states having about 2 to 3 eV higher energy due to the lower-than-octahedral crystal field at the copper sites. However, excitations to these higher energy states observed with RIXS show indications of strong coupling to doped holes in the 3dx2−y2 band. This relaunches a decades-old question of the possible role of the orbital degrees of freedom that once motivated Bednorz and Müller to search for superconductivity in these systems. Here we explore a direction different from the Jahn–Teller electron–phonon coupling considered by Bednorz and Müller, namely the interaction between holes mediated by dd excitations.

Female naïve human pluripotent stem cells carry X chromosomes with Xa-like and Xi-like folding conformations.

Three-dimensional (3D) genomics shows immense promise for studying X chromosome inactivation (XCI) by interrogating changes to the X chromosomes' 3D states. Here, we sought to characterize the 3D state of the X chromosome in naïve and primed human pluripotent stem cells (hPSCs). Using chromatin tracing, we analyzed X chromosome folding conformations in these cells with megabase genomic resolution. X chromosomes in female naïve hPSCs exhibit folding conformations similar to the active X chromosome (Xa) and the inactive X chromosome (Xi) in somatic cells. However, naïve X chromosomes do not exhibit the chromatin compaction typically associated with these somatic X chromosome states. In H7 naïve human embryonic stem cells, XIST accumulation observed on damaged X chromosomes demonstrates the potential for naïve hPSCs to activate XCI-related mechanisms. Overall, our findings provide insight into the X chromosome status of naïve hPSCs with a single-chromosome resolution and are critical in understanding the unique epigenetic regulation in early embryonic cells.

Enhanced pH‐Universal Hydrogen Evolution Reactions on the Ru/a–Ni–MoO3 Electrocatalysts

Green hydrogen production through the electrocatalytic hydrogen evolution reaction (HER) is a promising solution for transition from fossil fuels to renewable energy. To enable the use of a variety of electrolytes with different pH values, HER catalysts with pH universality are highly desirable but their performance remains mediocre. Herein, a pH‐universal HER catalyst composed of ruthenium nanoparticles decorated on amorphous Ni‐doped MoO3 (a–Ni–MoO3) nanowire support is reported, that is, Ru/a–Ni–MoO3, which achieves enhanced performance as compared to the commercial Ru/C catalyst. Electron transfer from Ru to a–Ni–MoO3 is identified by spectroscopic techniques, which results in a modified electronic structure of the Ru active sites with a reduced electron density of 4d states near the Fermi level. Density functional theory calculations further reveal that the modulated electronic structure weakens the interactions between the Ru active sites and the reaction intermediates, which facilitates the HER reaction steps including H intermediate desorption and water dissociation. Experimental and theoretical findings provide insight into enhancing pH‐universal HER performance through modulation of electrocatalyst electronic structure.

Differentiating the bonding states in calcium carbonate polymorphs by low-loss electron-energy-loss spectroscopy

Calcium carbonate is one of the important building components in organisms, especially the two most common polymorphs, calcite and aragonite. Here, to understand the difference in bonding state, the two polymorphs are characterized by valence (low-loss) electron energy loss spectroscopy. It is found that the difference in Ca M23 edge originating from 3p to 3d states is consistent with the change of Ca-O bonds in the two studied polymorphs. Surprisingly, the measured Ca M23 edge is in qualitative agreement with the calculated partial density of states (PDOS) of Ca-d states in contrast to their L edges (from 2p to 3d states) which are strongly influenced by atomic multiplet effect (spin-orbit coupling). This is because the atomic multiplet effect is much reduced for the Ca 3p orbital, which permits the corresponding Ca M23 edge to be compared with the PDOS results. Our findings show insights that PDOS can potentially be used to interpret the M23 edge of lighter 3d transition metals such as scandium, titanium, vanadium and chromium when such interpretation may not be achieved for their L edges.

Band-Gap Energy and Electronic d-d Transitions of NiWO4 Studied under High-Pressure Conditions.

We report an extensive study of the optical and structural properties of NiWO4 combining experiments and density functional theory calculations. We have obtained accurate information on the pressure effect on the crystal structure determining the equation of state and compressibility tensor. We have also determined the pressure dependence of the band gap finding that it decreases under compression because of the contribution of Ni 3d states to the top of the valence band. We report on the sub-band-gap optical spectrum of NiWO4 showing that the five bands observed at 0.95, 1.48, 1.70, 2.40, and 2.70 eV correspond to crystal-field transitions within the 3d8 (t2g6eg2) configuration of Ni2+. Their assignment, which remained controversial until now, has been resolved mainly by their pressure shifts. In addition to the transition energies, their pressure derivatives are different in each band, allowing a clear band assignment. To conclude, we report resistivity and Hall-effect measurements showing that NiWO4 is a p-type semiconductor with a resistivity that decreases as pressure increases.

Resonant photoemission spectroscopy of atomic layer Fe2N on Cu(111) with continuous angular rotation of linearly polarized light

Linearly polarized soft x-rays provide information about electronic or magnetic anisotropy through absorption into materials or generation of photoelectrons. In order to change the relative angle between linear polarization and sample crystalline axes, either x-ray polarization or the sample needs to be rotated. Due to difficulties of polarization control in the soft x-ray range, a conventional approach was to rotate the sample. However, this method is not compatible, for example, with operando measurements on non-uniform samples where sample size and rotational motion are severely restricted. At BL07LSU of SPring-8, we developed a new method to rotate the linear polarization angle using a segmented cross undulator. We report an application of this linear polarization rotation to resonant photoemission spectroscopy on an magnetic atomic layer Fe2N on Cu(111) to probe the electronic anisotropy of the 3d states in the vicinity of the Fermi level.

The Influence of Halide Ion Substitution on Energy Structure and Luminescence Efficiency in CeBr2I and CeBrI2 Crystals.

This study aims to determine the optimum composition of the CeBr1-xIx compound to achieve the maximum light output. It is based on calculations of the band energy structure of crystals, specifically taking into account the characteristics of the mutual location of local and band 5d states of the Ce3+ ions. The band energy structures for CeBr2I and CeBrI2 crystals were calculated using the projector augmented wave method. The valence band was found to be formed by the hybridized states of 4p Br and 5p I. The 4f states of Ce3+ are located in the energy forbidden band gap. The conduction band is formed by the localized 5d1 states, which are created by the interaction between the 5d states of Ce3+ and the 4f0 hole of the cerium ion. The higher-lying delocalized 5d2 states of Ce3+ correspond to the energy levels of the 5d states of Ce3+ in the field of the halide Cl0 (Br0) hole. The relative location of 5d1 and 5d2 bands determines the intensity of 5d-4f luminescence. The bottom of the conduction band is formed by localized 5d1 states in the CeBr2I crystal. The local character of the bottom of the conduction band in the CeBr2I crystal favors the formation of self-trapped Frenkel excitons. Transitions between the 5d1 and 4f states are responsible for 5d-4f exciton luminescence. In the CeBrI2 crystal, the conduction band is formed by mixing the localized 5d1 and delocalized 5d2 states, which leads to quenching the 5d-4f luminescence and a decrease in the light output despite the decrease in the forbidden band gap. CsBr2I is the optimum composition of the system to achieve the maximum light output.

Magnetic properties of Cr-doped VO2 thin films in tetragonal phase of rutile and their synchrotron-based electronic structures

The present study is focused on the investigation at 400 K of the tetragonal-rutile phase of Cr-doped VO2 (CVO) thin films grown by pulsed laser deposition. Synchrotron-based x-ray measurements of both the surface-sensitive total electron yield (TEY) and bulk-sensitive total fluorescence yield (TFY) modes were used to investigate the pristine and Cr-doped VO2 (5%, 10%, 20%, and 30% of atomic weight). The structural analysis and purity of the crystalline phase of the as-deposited films are manifested via grazing incidence x-ray diffraction patterns, which confirm the tetragonal-rutile phase. The purity of the phase is also confirmed by the presence of Eg-mode phonons in the Raman spectra and its deconvolution reflects on the oxygen-mediated electronic/vibrational transitional effect. A clear hysteretic behavior obtained through vibrating sample magnetometry strongly suggests the ferromagnetic interaction in the thin films of CVO. The local-electronic property of the samples is examined using x-ray absorption spectroscopy (XAS) in TEY and TFY modes where the difference in the configured helicity photons resulted in the fine spectra of x-ray magnetic circular dichroism (XMCD). XAS and XMCD measurements performed at V L2,3 and Cr L2,3 edges explicitly demonstrate the ferromagnetism in the thin films of CVO. The strong hybridization between V 3d and Cr 3d states with O 2p states is evident from the spectra of the O K-edge, resulting in the onset of the cation-pair formation V5+–Cr3+, which is ferromagnetic by means of double-exchange interaction. The theoretical calculation of density functional theory made upon Vienna ab initio simulation package suggests that CVO is in a mixed state of a ferromagnetic-insulator and a half-metallic ferromagnet.