Complex Stacking Research Articles

Incorporating thermal co-evaporation in current-matched all-perovskite triple-junction solar cells.

Thermal co-evaporation of halide perovskites is a solution-free, conformal, scalable, and controllable deposition technique with great potential for commercial applications, particularly in multi-junction solar cells. Monolithic triple-junction perovskite solar cells have garnered significant attention because they can achieve very high efficiencies. Nevertheless, challenges arise in fabricating these devices, as they require multiple layers and precise current matching across complex absorber stacks. Here we demonstrate a current-matched monolithic all-perovskite p-i-n triple-junction solar cell enabled by controlled thermal co-evaporation of various absorber layers in the stack. The top and middle subcells were fabricated by developing optimized thermally co-evaporated Cs0.3FA0.7Pb(I0.56Br0.44)3 (1.80 eV bandgap) and FAPbI3 (1.53 eV) perovskites, respectively, while the bottom subcell employed a solution-processed Cs0.25FA0.75Pb0.5Sn0.5I3 (1.25 eV) perovskite. By optimising absorber thicknesses and compositions through optical modelling, we achieve excellent current matching between the top (9.6 mA cm-2), middle (9.3 mA cm-2), and bottom subcells (9.0 mA cm-2), achieving an overall efficiency of 15.8%. Optical modelling simulations suggest that current matching and efficiency up to 11.4 mA cm-2 and 37.6% respectively could be attainable using the latest interlayer materials. This work highlights the potential of scalable vapour-based deposition techniques for advancing multi-junction perovskite-based solar cells, paving the way for future developments in this field.

Block copolymer-assembled nanopore arrays enable ultrasensitive label-free DNA detection.

DNA detection via nanoporous-based electrochemical biosensors is a promising method for rapid pathogen identification and disease diagnosis. These sensors detect electrical current variations caused by DNA hybridization in a nanoporous layer on an electrode. Current fabrication techniques for the typically micrometers-thick nanoporous layer often suffer from insufficient control over nanopore dimensions and involve complex fabrication steps, including handling and stacking of a brittle porous membrane. Here, we introduce a bottom-up fabrication process based on the self-assembly of high molecular weight block copolymers with sol-gel precursors to create an inorganic nanoporous thin film directly on electrode surfaces. This approach eliminates the need for elaborate manipulation of the nanoporous membrane, provides fine control over the structural features, and enables surface modification with DNA capture probes. Using this nanoarchitecture with a thickness of 150 nm, we detected DNA sequences derived from 16S rRNA gene fragments of the E. coli genome electrochemically in less than 20 minutes, achieving a limit of detection of 30 femtomolar (fM) and a limit of quantification of 500 fM. This development marks a significant step towards a portable, rapid, and accurate DNA detection system.

Stability of high energy superlattice faults in Ni-based superalloys from atomistic simulations

High energy stacking faults generated by lattice dislocations entering the strengthening precipitates of Ni-based superalloys are responsible for the unique mechanical properties of these structural materials. However, the question about stability of these faults has not received the attention it deserves. Using atomistic simulations, we show that the anti-phase boundary (APB) can spontaneously transform into super intrinsic stacking fault (SISF) and the complex stacking fault (CSF) can spontaneously transform into L12 lattice structure. The former transformation explains the experimentally observed presence of isolated SISFs and super extrinsic stacking faults (SESFs) in the precipitates. Finally, multiple studies were focused on finding alloying additions which increase the APB and CSF energies. We demonstrate therefore that alloying additions which increase stacking fault energies may conversely decrease their stabilities.

Quantifying solid volume of stacked eucalypt timber using detection-segmentation and diameter distribution models

Accurate timber quantification is essential in forestry and the timber industry, impacting harvest planning, processing, pricing, and overall supply chain management. Traditional methods for estimating the volume of stacked timber, often reliant on manual measurements, are time-consuming and prone to error. This research aims to develop an accurate procedure for estimating the volume of stacked eucalypt timber in yards. The proposed procedure combines automatic log detection and diameter distribution models. Automatic log detection was achieved using advanced computer vision techniques, specifically the You Only Look Once version 9 (YOLOv9) model, which automates the identification and counting of individual logs within a stack. We used stem diameter distribution models to estimate total stack volume based on log counts and probability densities. This approach ensures high accuracy and efficiency, significantly reducing the time and effort required for volume estimation. The dataset used for this study includes diameter measurements from a pre-harvest inventory of eucalypt trees aged 6 and 7 years, alongside videos of stacked timber. The YOLOv9 model was trained to detect logs from these videos, achieving high precision in object detection and segmentation tasks. Performance metrics such as Box Precision, Box Recall, and mean Average Precision (mAP) were used to evaluate the model's effectiveness. The results indicate that the model generalizes well to new data, with high accuracy in both validation and test sets. Among the distribution models evaluated, the generalized extreme value (GEV) distribution provided the best fit for the stem diameter data, allowing for accurate volume predictions. This procedure, which integrates automatic log detection with diameter distribution models, offers a scalable solution applicable to large and complex timber stacks. Finally, a repository was established to allow users to test the proposed method. Future works will focus on refining the model's accuracy and expanding its applicability across different species, forest production and log conditions.

A Supramolecular‐Nanocage‐Based Framework Stabilized by π‐π Stacking Interactions with Enhanced Photocatalysis

Abstractπ frameworks, defined as a type of porous supramolecular materials weaved from conjugated molecular units by π‐π stacking interactions, provide a new direction in photocatalysis. However, such examples are rarely reported. Herein, we report a supramolecular‐nanocage‐based π framework constructed from a photoactive Cu(I) complex unit. Structurally, 24 Cu(I) complex units stack together through π‐π stacking interactions, forming a truncated octahedral nanocage with sodalite topology. The inner diameter of the nanocage is 2.8 nm. By sharing four open faces, each nanocage connects with four equivalent ones, forming a 3D porous π framework (π‐2). π‐2 shows good thermal and chemical stability, which can adsorb CO2, iodine, and methyl orange molecules. More importantly, π‐2 can serve as a photocatalyst for hydrogen evolution reaction. With ultrafine Pt subnanometer particles (0.9±0.1 nm) incorporated into the nanocages as a co‐catalyst, the hydrogen evolution rate reaches a record‐high value of 524012 μmol/gPt/h in the absence of any additional photosensitizers. The high photocatalytic activity can be ascribed to the ultrafine size of the Pt particles, as well as the fast electron transfer from π‐2 to the highly active Pt upon illumination. π‐2 represents the unique stable supramolecular‐cage‐based π framework with excellent photocatalytic activity.

A Supramolecular-Nanocage-Based Framework Stabilized by π-π Stacking Interactions with Enhanced Photocatalysis.

π frameworks, defined as a type of porous supramolecular materials weaved from conjugated molecular units by π-π stacking interactions, provide a new direction in photocatalysis. However, such examples are rarely reported. Herein, we report a supramolecular-nanocage-based π framework constructed from a photoactive Cu(I) complex unit. Structurally, 24 Cu(I) complex units stack together through π-π stacking interactions, forming a truncated octahedral nanocage with sodalite topology. The inner diameter of the nanocage is 2.8 nm. By sharing four open faces, each nanocage connects with four equivalent ones, forming a 3D porous π framework (π-2). π-2 shows good thermal and chemical stability, which can adsorb CO2, iodine, and methyl orange molecules. More importantly, π-2 can serve as a photocatalyst for hydrogen evolution reaction. With ultrafine Pt subnanometer particles (0.9±0.1 nm) incorporated into the nanocages as a co-catalyst, the hydrogen evolution rate reaches a record-high value of 524012 μmol/gPt/h in the absence of any additional photosensitizers. The high photocatalytic activity can be ascribed to the ultrafine size of the Pt particles, as well as the fast electron transfer from π-2 to the highly active Pt upon illumination. π-2 represents the unique stable supramolecular-cage-based π framework with excellent photocatalytic activity.

Shaping corticospinal pathways in virtual reality: effects of task complexity and sensory feedback during mirror therapy in neurologically intact individuals

BackgroundRestoration of limb function for individuals with unilateral weakness typically requires volitional muscle control, which is often not present for individuals with severe impairment. Mirror therapy—interventions using a mirror box to reflect the less-impaired limb onto the more-impaired limb—can facilitate corticospinal excitability, leading to enhanced recovery in severely impaired clinical populations. However, the mirror box applies limitations on mirror therapy, namely that all movements appear bilateral and are confined to a small area, impeding integration of complex activities and multisensory feedback (e.g., visuo-tactile stimulation). These limitations can be addressed with virtual reality, but the resulting effect on corticospinal excitability is unclear.ObjectiveExamine how virtual reality-based unilateral mirroring, complex activities during mirroring, and visuo-tactile stimulation prior to mirroring affect corticospinal excitability.Materials and methodsParticipants with no known neurological conditions (n = 17) donned a virtual reality system (NeuRRoVR) that displayed a first-person perspective of a virtual avatar that matched their motions. Transcranial magnetic stimulation-induced motor evoked potentials in the nondominant hand muscles were used to evaluate corticospinal excitability in four conditions: resting, mirroring, mirroring with prior visuo-tactile stimulation (mirroring + TACT), and control. During mirroring, the movements of each participant’s dominant limb were reflected onto the nondominant limb of the virtual avatar, and the avatar’s dominant limb was kept immobile (i.e., unilateral mirroring). The mirroring + TACT condition was the same as the mirroring condition, except that mirroring was preceded by visuo-tactile stimulation of the nondominant limb. During the control condition, unilateral mirroring was disabled. During all conditions, participants performed simple (flex/extend fingers) and complex (stack virtual blocks) activities.ResultsWe found that unilateral mirroring increased corticospinal excitability compared to no mirroring (p < 0.001), complex activities increased excitability compared to simple activities during mirroring (p < 0.001), and visuo-tactile stimulation prior to mirroring decreased excitability (p = 0.032). We also found that these features did not interact with each other.DiscussionsThe findings of this study shed light onto the neurological mechanisms of mirror therapy and demonstrate the unique ways in which virtual reality can augment mirror therapy. The findings have important implications for rehabilitation for design of virtual reality systems for clinical populations.

An Efficient Method to Compute Capillary Pressure Functions and Saturation-Dependent Permeabilities in Porous Domains Spanning Several Length Scales

A method for calculating capillary pressure functions and saturation-dependent permeabilities of geometries containing several length scales is presented. The method does not require the exact geometries of the smaller length scales. Instead, it requires the effective two-phase flow parameters. It does this by generating phase distributions that form static equilibria at a selected capillary pressure value, similar to pore-morphology methods. Within a porous material, the effective parameters are used to obtain the corresponding phase saturation. It is shown how these phase distributions can be used in geometries spanning several length scales to calculate the capillary pressure function and saturation-dependent permeabilities. The method is tested on a geometry containing a simple isotropic porous material and it is applied to a complex textile stack geometry from a liquid composite molding process. In this geometry, three different length scales can be distinguished. The effective two-phase flow parameters of the textile stack are calculated by the proposed method, avoiding expensive simulations.

Constructing Alkyl Chain Modified FeII Spin Crossover Complexes through Complementary Pair Strategy

AbstractFour alkyl chains and cyclohexane modified FeII complexes [Fe(Ln)(L’)](ClO4)2⋅solv (n=1, 2, 3, 4) were synthesized and characterized. X‐ray diffraction study showed that these complexes were constituted by asymmetric mononuclear FeII entities, incorporating alkyl‐chain‐modified bppCOOH (2,6‐bis(1H‐pyrazol‐1‐yl)isonicotinic acid) ligands and 6,6’’‐2,6‐dimethoxyphenyl‐substituted terpy ligand (L’). Magnetic susceptibility measurements revealed that complexes 1, 2, and 3 were in the high spin state across the measured temperature range, whereas complex 4 displayed an incomplete spin crossover phenomenon, with a transition temperature (T1/2) at 240 K. Investigations into variable‐temperature structure and magneto‐structural correlations revealed that the integration of alkyl‐chain‐modified bipyridyl units fostered the π⋅⋅⋅π intra‐ and intermolecular interactions, contributing to distinct crystal stacking and spatial configurations in complex 4 when compared to its counterparts. These findings underscore the pivotal influence of intramolecular interactions on the FeII spin states and highlight the significance of designing flexible ligands for modulating spin‐crossover characteristics.

Crystal structure of tris-{N,N-diethyl-N'-[(4-nitro-phen-yl)(oxo)meth-yl]carbamimido-thio-ato}cobalt(III).

The synthesis, crystal structure, and a Hirshfeld surface analysis of tris-{N,N-diethyl-N'-[(4-nitro-phen-yl)(oxo)meth-yl]carbamimido-thio-ato}cobalt(III) conducted at 180 K are presented. The complex consists of three N,N-diethyl-N'-[(4-nitro-benzene)(oxo)meth-yl]carbamimido-thio-ato ligands, threefold sym-metric-ally bonded about the CoIII ion, in approximately octa-hedral coordination, which generates a triple of individually near planar metallacyclic (Co-S-C-N-C-O) rings. The overall geometry of the complex is determined by the mutual orientation of each metallacycle about the crystallographically imposed threefold axis [dihedral angles = 81.70 (2)°] and by the dihedral angles between the various planar groups within each asymmetric unit [metallacycle to benzene ring = 13.83 (7)°; benzene ring to nitro group = 17.494 (8)°]. The complexes stack in anti-parallel columns about the axis of the space group (P), generating solvent-accessible channels along [001]. These channels contain ill-defined, multiply disordered, partial-occupancy solvent. Atom-atom contacts in the crystal packing predominantly (∼96%) involve hydrogen, the most abundant types being H⋯H (36.6%), H⋯O (31.0%), H⋯C (19.2%), H⋯N (4.8%), and H⋯S (4.4%).

Symmetry breaking induced asymmetric dislocation-planar fault interactions in ordered intermetallic alloys

In this study, we present the first comprehensive examination of symmetry breaking in the interactions between dislocation and superlattice planar faults, including anti-phase boundary (APB), complex stacking fault (CSF), superlattice intrinsic stacking fault (SISF), to reveal the underlying asymmetric dislocation reaction mechanisms depending on the sense of applied stress, employing both large-scale atomistic simulations and continuum dislocation theory. Four ordered intermetallic alloy systems including γ−Ni/γ′−Ni3Al and γ−Ni/γ′−Ni3Fe, γ−Al/γ−TiAl, and α−Ti/α2−Ti3Al were selected as the representative model systems, with two primary symmetry breaking effects, i.e., translational and three-fold rotational symmetry breaking considered. Detailed atomic steps of asymmetrical dislocation reactions and the corresponding asymmetrical dislocation bypassing mechanisms of precipitation have been elucidated, shown to be highly dependent on the geometrical configuration of the precipitate and the relative magnitudes of APB, CSF and SISF fault energies. A continuum model framework was then developed, which, for the first time, provides accurate and quantitative predictions of the threshold conditions triggering critical asymmetrical dislocation slips, verified to be in good agreement with the simulation results. Our study also successfully reproduced the experimentally observed dislocation-induced APB-SISF transformation, with a new dislocation reaction mechanism proposed to explain the transformation process. The findings are expected to be a key enabling stepstone for future innovation in intermetallic alloys strengthened through ordered phases for advanced applications in aeronautic and automotive industries.

Multi-scale modelling of an electrodialysis with bipolar membranes pilot plant and economic evaluation of its potential

Sodium hydroxide and hydrochloric acid are widely used chemicals in different industrial sectors. To minimize costs and risks associated with transportation, handling and storage, these hazardous chemicals can be produced in situ employing electrodialysis with bipolar membranes (EDBM). This work presents a multi-scale model capable of simulating large scale EDBM units with complex stack configuration (i.e., internal staging) that can be used to design and optimize the process. The model was validated in two different process configurations using experimental results obtained from an EDBM pilot plant. Discrepancies between model and experimental results in the range of 2–11 % were obtained. The validated model was used to conduct a techno-economic evaluation adopting the feed and bleed configuration. Results show that current efficiency increases as the current density rises. At 600 A m−2, values of current efficiency between 72 % and 96 % were found for sodium hydroxide concentration in the range of 0.5–1 mol L−1. The levelized cost of sodium hydroxide (LCoNaOH) was evaluated, in the same range of concentrations, demonstrating that values between 280 and 370 € ton−1 can be obtained, fixing the electricity prince (0.1 kWh kg−1) and the triplet specific cost (600 US$ m−2). Moreover, assuming a reduced cost of electricity and triplet to 0.05 kWh kg−1 and 300 US$ m−2, respectively, an absolute minimum of 140 € ton−1 was found for the target 0.5 mol L−1. A double stage EDBM configuration was simulated to show the scale-up potentials of the multi-scale model. A reduction in the LcoNaOH of 10 % was obtained for a target concentration of 1 mol L−1. These results prove the attractiveness of the EDBM technology for producing in situ chemicals.

Zipserite, a new bismuth chalcogenide Bi5(S,Se)4 from Nagybörzsöny in Hungary with a R$\bar{3}$m(00γ)00 modulated structure

AbstractZipserite is a new mineral species discovered in a sample collected from the old mine dumps of the abandoned epithermal deposit Nagybörzsöny in Hungary. Zipserite occurs as anhedral to subhedral, lath-like grains, up to 500 μm in size, in hydrothermally strongly altered rocks. It is found at a contact between bismuth and bismuthinite, also associated with rare ikunolite and joséite-A. Zipserite is silvery white with a metallic lustre. Mohs hardness is ca. 2–3 and the calculated density is 7.815 g.cm–3. In reflected light, zipserite is grey–white, with colour and reflectance essentially matching those of bismuthinite. Bireflectance is weak, internal reflections not present. Anisotropy is moderately strong, with dark blue and grey colours of anisotropy. Reflectance values for the four Commission on Ore Mineralogy wavelengths of zipserite in air [Rmax, Rmin (%) (λ in nm)] are: 48.4, 46.4 (470); 47.8, 45.9 (546); 47.8, 45.8 (589); and 47.5, 45.6 (650). The empirical formula, based on electron-microprobe analyses, is (Bi4.74Pb0.31)Σ5.05(S3.38Se0.56Te0.02)Σ3.96, that can be simplified as Bi5(S,Se)4. The ideal end-member formula of zipserite is Bi5S4, which requires Bi 89.07 and S 10.93, total 100 wt.%. Zipserite possesses a fascinating crystal structure. The average structure is trigonal, with space group P$\bar{3}$m, a = 4.162(1) Å, c = 16.397(1) Å, V = 245.94(4) Å3 and Z = 2. The structure is built by the alternation of a double bismuth layer Bi2 and the Bi3S4 block which is a three octahedra thick layer. Its general formula can be expressed as Bi2 + Bi3S4, which corresponds directly to the observed stacking. At 98 K, the structure can be described using the superspace formalism with an R-centred trigonal unit cell a = 4.209(2) Å, c0 = 5.616(6) Å, a modulation vector q ≈ 4/3 c* and the superspace group R$\bar{3}$m(00γ)00. Zipserite is not only a new mineral but also the first named member of a new sub-group of compounds within the broader family of bismuth chalcogenides, characterised by complex stacking of structural units (Bi2 layers and Bi3S4 blocks). Some of these phases are being investigated as promising thermoelectric materials and synthetic analogues of zipserite could also be inspected for similar physical properties.

Inverse design of twisted bilayer graphene metasurface for terahertz absorption broadening based on artificial neural network

With the development of terahertz (THz) technology, achieving ultra-wideband absorption of THz waves has become a significant challenge that researchers are striving to address. Different from the complex stacking of multiple graphene layers in the traditional design, inspired by the twisted magic angle of graphene structures, a twisted bilayer graphene metasurface absorber (TBGMA) is innovatively investigated for THz wave absorption broadening inverse design based on artificial neural network (ANN). Compared with the traditional manual parameter tuning, the ANN-based inverse design method can quickly accomplish the selection of the structural parameters and twist angles of the TBGMA, realizing the ultra-wideband absorption of THz waves (6.046 THz). The relationship between twisted SGLs and broadened effective absorption bandwidths is thoroughly analyzed through a combination of the electric field distribution and effective medium theory (EMT). Additionally, the tunability and absorption spectra of TBGMA under different incidence conditions have been discussed. The study of the twisted angle of SGLs can provide a unique idea for expanding the absorption bandwidth, and the inverse design of structural and angle parameters in conjunction with ANN is expected to be extended to the design of other precision structures in nanophotonics.

Enhancing the stability of zein pickering foams via hydrophilic reassembly with sugar alcohols and glycosides: A structural and molecular investigation

Sucralose (Suc), maltitol (Mal), mannitol (Man), and stevioside (Ste) — a group of alcohol-soluble sugar derivatives with different contents and molecular configurations of hydrophilic groups — were complexed with deaminated zein to significantly enhance the stability of zein-based Pickering foams and develop new composite coacervates to replace animal protein-based foams. Compared with Suc, Mal, and Man, Ste induced better hydrophilic reassembly in zein by forming stronger van der Waals forces and hydrogen bonds, leading to optimum foamability (+160.66%) and foam stability (+17.11%). Moreover, it increased the solubility (+0.07 mg/mL) and decreased the surface hydrophobicity index (−24.88) of zein. These enhancements could primarily be attributed to alterations in the aggregation conformation and hydrophobic interactions within Ste/ZN. Subsequently, SEM and CLSM confirmed that due to the amphiphilic structure of Ste, dispersed zein micelles could aggregate into complex stacking structures. The increase in random coils (+2.48%) and β-sheets (+2.93%) indicated the enhanced flexibility of the zein chain, thereby facilitating zein adsorption and unfolding at the air-water interface. Moreover, molecular simulation demonstrated that an average of 3.1 hydrogen bonds were formed between zein and Ste, and the average binding free energy was −14.20 kcal/mol. These findings provide novel evidence and theoretical guidance for the development of highly stable plant protein-based food foams. The enhancement of Pickering foam stability holds significant implications for the storage and development of high-performance food foams.

Validity constraints for data analysis workflows

Porting a scientific data analysis workflow (DAW) to a cluster infrastructure, a new software stack, or even only a new dataset with some notably different properties is often challenging. Despite the structured definition of the steps (tasks) and their interdependencies during a complex data analysis in the DAW specification, relevant assumptions may remain unspecified and implicit. Such hidden assumptions often lead to crashing tasks without a reasonable error message, poor performance in general, non-terminating executions, or silent wrong results of the DAW, to name only a few possible consequences. Searching for the causes of such errors and drawbacks in a distributed compute cluster managed by a complex infrastructure stack, where DAWs for large datasets typically are executed, can be tedious and time-consuming.We propose validity constraints (VCs) as a new concept for DAW languages to alleviate this situation. A VC is a constraint specifying logical conditions that must be fulfilled at certain times for DAW executions to be valid. When defined together with a DAW, VCs help to improve the portability, adaptability, and reusability of DAWs by making implicit assumptions explicit. Once specified, VCs can be controlled automatically by the DAW infrastructure, and violations can lead to meaningful error messages and graceful behavior (e.g., termination or invocation of repair mechanisms). We provide a broad list of possible VCs, classify them along multiple dimensions, and compare them to similar concepts one can find in related fields. We also provide a proof-of-concept implementation for the workflow system Nextflow.

21.2% GaAs Solar Cell Using Bilayer Electron Selective Contact

GaAs remains one of the crucial materials for solar cell applications as it boasts the world's highest efficiency single‐junction solar cells. However, their high cost limits their widespread terrestrial applications. Traditional GaAs solar cells require a complex stack of doped junctions, which can only be grown using epitaxy, which is a very costly technique. Herein, a nonepitaxial bilayer of ZnO and TiO2 as electron‐selective contact is studied. It is shown that a bilayer selective contact can achieve very high performance through interface band engineering and a reduction of the barrier for electron transfer. 21.2% efficient solar cells is achieved, with Voc of 1.04 V, Jsc of 26.13 mA cm−2, and a fill factor of 77.8%. The Voc reported in the article is comparable to the highest Voc reported for substrate‐based GaAs solar cells of 1.075 V. An experimental loss analysis shows that the device is mainly limited by series and shunt resistance and reflection losses, both of which can further be minimized by optimization of the fabrication process. The results presented will be very useful for the further development of cheaper GaAs solar cells, whereas the bilayer selective contact concept can be implemented for other kinds of solar cells.

Four‐Dimensional Design Space of High‐Q Second‐Order Distributed Feedback Perovskite Lasers

AbstractSecond‐order distributed feedback (DFB) resonators are widely used for thin‐film lasers as they combine low lasing thresholds with ease of manufacturing. Here, the grating design parameters are varied to map the lasing characteristics of lead halide perovskite films deposited on a single substrate that contains hundreds of high‐quality silicon nitride surface gratings. The lowest lasing threshold (≈130 µJ cm−2) is identified through the aid of near‐field and far‐field imaging spectroscopy in a four‐dimensional design space composed of grating period, duty cycle, active layer thickness, and cavity length. Moreover, it is shown that antisymmetric modes support high‐quality lasing (Q up to ≈10800) in the second‐order DFBs. The multi‐dimensional experimental analysis is accompanied by a thorough theoretical study with a semi‐empirical model based on coupled wave equations, which is used to investigate the lasing characteristics beyond the manufacturing range. The results can be applied to a broad range of thin‐film DFB resonators, enabling the design of more complex laser stack configurations including light‐emitting devices for current‐injection lasing.

superdislocation mobility with different character angles in Ni3Al

The glide of <110>/{111} superdislocations in Ni3Al becomes prevalent in tertiary creep and take a dominant role in influencing the creep resistance of Ni-based single crystal superalloys at the tertiary stage. Here we carried out atomistic simulations to investigate the mobility law of screw, 30° mixed, 60° mixed and edge <110> superdislocations in Ni3Al. Based on the Peierls-Nabarro model, we found that the distance of the dissociated anti-phase boundary (APB) and complex stacking fault (CSF) of <110> superdislocations increases with increasing the character angle (from screw to edge), keeping a good accordance with the analysis by anisotropic elastic theory. We further study the motion of the superdislocations at temperatures ranging from 300 K to 1000 K. The dislocation mobility is distinct to its character angle, i.e., the edge-like (30° and 90°) superdislocations have a higher speed than the screw-like (0° and 60°) superdislocations. For all types of superdislocations, the drag coefficient increases linearly with increasing temperature in the phonon-drag regime, while behaves to be independent on temperature in the asymptotic regime. Finally, we explored the origin of mobility disparity between the edge-like and screw-like superdislocations in terms of energy landscape for the dislocation glide. We observed that the two 1/2<110> dissociated superpartials move coordinately in edge-like superdislocations with no variation of APB ribbon width. However, the motion of two superpartials are uncorrelated in screw-like superdislocations with the expansion and reduction of APB, resulting in a relatively higher Peierls barrier. Our present work could help to understand the creep failure in Ni-based single crystal superalloys.

Accurate complex-stacking-fault Gibbs energy in Ni3Al at high temperatures

To gain a deeper insight into the anomalous yield behavior of Ni3Al, it is essential to obtain temperature-dependent formation Gibbs energies of the relevant planar defects. Here, the Gibbs energy of the complex stacking fault (CSF) is evaluated using a recently proposed ab initio framework [Acta Materialia, 255 (2023) 118986], accounting for all thermal contributions—including anharmonicity and paramagnetism—up to the melting point. The CSF energy shows a moderate decrease from 300K to about 1200K, followed by a stronger drop. We demonstrate the necessity to carefully consider the individual thermal excitations. We also propose a way to analyze the origin of the significant anharmonic contribution to the CSF energy through atomic pair distributions at the CSF plane. With the newly available high-temperature CSF data, an increasing contribution to the energy barrier for the cross-slip process in Ni3Al with increasing temperature is unveiled, necessitating the refinement of existing analytical models.