Defect Energy Research Articles

Burgers tensor flow accounting for cold work and thermal annealing

This paper proposes a kinematical-thermal-based constitutive law for the evolution of Burgers tensor during cold work and upon subsequent thermal annealing of a polycrystalline. The proposal is based on the paper by Anand et al. [L. Anand., M. E. Gurtin., B. D. Reddy, The stored energy of cold work, thermal annealing, and other thermodynamic issues in single crystal plasticity at small length scales, Int. J. Plast. 64 (2015), 1?25]. The principle of virtual work and thermodynamic laws are employed to obtain balance of forces, balance of energy, and free-energy imbalance. Non-recoverable energetic microscopic stresses are obtained as features for materials that are cold-worked whenever the defect energy is dependent on Burgers tensor. Consequently, it is observed that internal-energetic plastic power is not less than entropic plastic power. The recovery rate during thermal annealing is shown to mimic dissipative behavior, leading to a reduction in the accumulation of dislocation densities. Furthermore, the free energy function ?approximated as a quadratic form? is used to obtain the constitutive relations for the macroscopic and microscopic stresses.

A first-principles study of the electronic structure and point defects in higher manganese silicide Mn4Si7.

Point defects play a crucial role in determining the physical properties of solid-state semiconductor materials. However, theoretical investigations dedicated to point defects in higher manganese silicides (HMSs), promising thermoelectric materials composed of earth-abundant and eco-friendly elements, are surprisingly absent in the literature. Here, using first-principles calculations we systematically investigate the intrinsic and extrinsic point defects in a HMS, Mn4Si7. Our results indicate that the formation energies of intrinsic defects in Mn4Si7 are sufficiently high to preclude their significant concentration under thermal equilibrium growth conditions, and the experimentally observed p-type conductivity of the pure HMS could be a result of self-doping. Additionally, we calculated the defect formation energies of 14 candidate dopants by fully considering the secondary phases, which are in good agreement with experimental findings. Our results provide valuable guidance for optimizing the doping strategy of HMSs for device applications.

Effect of temperature on the structure, catalyst and magnetic properties of un-doped zinc oxide nanoparticles: experimental and DFT calculation.

Zinc oxide nanoparticles were synthesized using sol-gel and hydrothermal techniques and characterized at different calcination temperatures (400, 500, and 600 °C). The study included an analysis of morphology, crystalline phase, particle size, elemental analysis, specific surface area and chemical state. Various characterization methods were employed, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), surface analysis (BET), nitrogen absorption and desorption (N2-desorption), Fourier transform infrared spectroscopy (FTIR), thermal analysis (TGA-DSC), temperature-programmed reduction of hydrogen (H2-TPR). Additionally, magnetic properties ZnO nanoparticles were investigated by electron spin resonance (ESR). The investigation revealed changes in reduction behavior, electron spin states, and magnetic properties. The interplay between defects, crystallization, and stability underscores the complexity of ZnO-NPs. These findings contribute to our understanding of nanomaterials and their potential applications in various fields. Density Functional Theory (DFT) calculations with a Hubbard U correction were performed to investigate native defects in ZnO and ZnOCH structures under oxygen-poor (low temperature), oxygen-rich (high temperature) and equilibrium (average temperature) conditions. The formation energies of native defects were calculated, and ESR spectra were simulated to analyze the presence and absence of C[double bond, length as m-dash]O, C-O, CH, and OH bands, as well as to identify the native defects present during growth. The results of the formation energy calculations and the simulated ESR spectra showed that the growth environment influences the native defects that occur during the ZnO preparation process. Inconsistencies between the calculation of formation energy and the ESR spectra suggested that the C[double bond, length as m-dash]O, C-O, CH, and OH bands were negligible and could be disregarded in the ZnO nanoparticles. The findings from this study contribute to a deeper understanding of ZnO-NPs, enabling the optimization of their properties for specific applications, such as effective catalysts in chemical reactions.

First-principles calculations of point defect migration mechanisms in InP

As an important second-generation semiconductor material, indium phosphide (InP) possesses excellent advantages such as a wide bandgap, high electron mobility, high photoelectric conversion efficiency, and strong radiation resistance. It is considered an excellent material for electronic devices in aerospace applications. However, point defects generated by space radiation particles in InP electronic devices can cause their electrical performance to degrade severely. In this study, first-principles calculations are employed to investigate the stable structures of point defects in InP and calculate the migration energy values of nearest-neighbor defects. Four stable structures of In vacancies and three stable structures of P vacancies are identified by constructing the stable structures of point defects in different charge states. The migration process of vacancy defects is studied, revealing that the migration energy of P vacancies is higher than that of In vacancies. Moreover, charged vacancy defects exhibit higher migration energy values than neutral vacancies. Regarding the migration process of interstitial defects, it is found that the migration energy of interstitial defects is smaller than that of vacancy defects. In the calculation of In interstitial migration process with different charge states, two different migration processes are found. Besides, during the migration calculations of P interstitial, a special intermediate state is discovered, resulting in multiple paths migrating to the nearest-neighbor position in the migration energy barrier diagram. The research results are helpful to understand the formation mechanism and migration behavior of defects in InP materials, and are important in designing and manufacturing InP devices with long-term stable operation in space environment.

N-type Ag2S modified CZTSSe solar cell with lowest Voc,def

One of the primary challenges impeding the efficiency improvement of kesterite (CZTSSe) solar cells is the significant open-circuit voltage deficit (Voc,def), mainly due to high defect concentrations and energy level...

Effect of fission defects on tensile strength of U3Si2 Σ5(210) grain boundary from first-principles calculations.

U3Si2 is regarded as a promising accident tolerant fuel (ATF) to replace the commercial fuel UO2; however, grain boundary (GB) embrittlement of U3Si2 caused by irradiation-induced defect segregation remains to be clarified. In this work, the U3Si2 Σ5(210) symmetrically tilted GB is taken as a representative to elucidate the individual effect of xenon (Xe) and vacancy on the tensile strength and failure of GBs using first-principles calculations. Compared with the predicted segregation energies of defects at the most energetically favourable positions of GBs, Si vacancy (VSi) has a much stronger preference to segregate to GBs than that of Xe substitution on the Si sublattice (XeSi). Moreover, the strengthening/embrittlement potency of GBs with single vacancy/Xe is evaluated using the first-principles-based uniaxial tensile test. Although both VSi and XeSi yield a weakening effect on the strength of the U3Si2 Σ5(210) GB, such defective GBs exhibit significantly stronger interface strengths compared to the corresponding defects segregated to the UO2 Σ3(111) GB. The underlying mechanism of strength change of U3Si2 GBs is discussed in terms of charge analysis. Our results can provide a fundamental understanding of the mechanical behavior of irradiated GBs from an atomic perspective.

Structural stability and electronic properties of charged point defects in monolayer blue phosphorus

As a new two-dimensional material, blue phosphorus has attracted considerable research interest due to its high carrier mobility and large bandgap. Although the structural defects of blue phosphorus have been discussed recently, the charged properties of these defects have not been explored. In this paper, using first-principles calculations based on density functional theory, the six most stable point defects and their corresponding charged states in blue phosphorus are studied, including Stone Wales (SW), single vacancy (SV), two double-vacancy (DV-1 and DV-2) and two substitution defects (O<sub>P</sub> and C<sub>P</sub>). The converged ionization energy values of charged defects in blue phosphorus are obtained by extrapolating the asymptotic expression of the energy dependent on the cell size. Subsequently, the formation energy values for different charge states are modified to determine their structural stabilities. Finally, their electronic properties are analyzed through band structures. The results suggest that SV<sup>1–</sup> is easy to ionize, owing to its lowest ionization energy (1.08 eV). Furthermore, among the defects we are considering, O<sub>P</sub><sup>1–</sup> is the most stable charged defect in blue phosphorus, with the lowest formation energy (–9.33 eV) under O-rich chemical potential condition. The negative formation energy indicates that O atoms can exist stably in blue phosphorus, implying that blue phosphorus is easily oxidized. The introduction of defect states will affect the bandgap of blue phosphorus, and the ionization of defects will cause the defect energy levels to shift, leading defects to transition between shallow and deep levels. This study provides theoretical guidance for the application of defect engineering in two-dimensional materials.

Atomic insight into the effects of precursor clusters on monolayer WSe2.

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have been attracting much attention due to their rich physical and chemical properties. At the end of the chemical vapor deposition growth of 2D TMDCs, the adsorption of excess precursor clusters onto the sample is unavoidable, which will have significant effects on the properties of TMDCs. This is a concern to the academic community. However, the structures of the supported precursor clusters and their effects on the properties of the prepared 2D TMDCs are still poorly understood. Herein, taking monolayer WSe2 as the prototype, we investigated the structure and electronic properties of SeN, WN (N = 1-8), and W8-NSeN (N = 1-7) clusters adsorbed on monolayer WSe2 to gain atomic insight into the precursor cluster adsorption. In contrast to W clusters that tightly bind to the WSe2 surface, Se clusters except for Se1 and Se2 are weakly adsorbed onto WSe2. The interaction between W8-NSeN (N = 1-7) clusters and the WSe2 monolayer decreases with the increase in the Se/W ratio and eventually becomes van der Waals interaction for W1Se7. According to the phase diagram, increasing the Se/W ratio by changing the experimental conditions will increase the ratio of SeN and W1Se7 clusters in the precursor, which can be removed by proper annealing after growth. W clusters induce lots of defect energy levels in the band gap region, while the adsorption of W1Se7 and SeN clusters (N = 3-6, 8) promotes the spatial separation of photo generated carriers at the interface, which is important for optoelectronic applications. Our results indicate that by controlling the Se/W ratio, the interaction between the precursor clusters and WSe2 as well as the electronic properties of the prepared WSe2 monolayer can be effectively tuned, which is significant for the high-quality growth and applications of WSe2.

Rational control of the typical surface defects of hybrid perovskite using tetrahexylammonium iodide.

There are numerous defects existing on the surface and grain boundary of perovskite, which adversely affect the performance and stability of perovskite solar cell devices. Systematic first-principles calculations show that the I vacancy (VI), Pb vacancy (VPb), Pb-I antisite (PbI), and I-Pb antisite (IPb) defects can significantly affect the electronic properties of the surface of formamidinium lead triiodide (FAPbI3); in particular the VPb, PbI and IPb surface defects can introduce defect energy levels in the band gap. Tetrahexylammonium iodide (THAI) that is strongly adsorbed on the (1 0 0) surface of FAPbI3 by forming Pb-I coordination bonds and I⋯H hydrogen bonds could eliminate or reduce the defect states near the band edge or in the band gap by transferring electrons between THAI and the surface of FAPbI3. In particular, the defect states introduced by VPb could be completely eliminated after the adsorption of THAI. This study shows an in-depth understanding of the influence of defects on the electronic properties of the surface of FAPbI3, as well as the passivation mechanism of organic salts on the surface defects of perovskite.

Inherent and induced defects in mixed-phase CuO nanoparticles

Copper (Cupric) oxide is a readily synthesized, non-toxic metal oxide with a wide range of uses, including the treatment of water, the manufacture of electronic devices, solar cells, cathodes for lithium-ion primary batteries, gas sensors, electrochromic devices, supercapacitors, and field effect transistors. The effects of Zn doping in CuO in three different concentrations (weights %) were investigated. The band gap and carrier concentration were altered due to the formation of defect energy states, lattice stresses, and the formation of ZnO, and Cu2O in addition to CuO. Temperature increases from room temperature resulted in the production of metal oxides with preferred crystal growth in specific orientations. An increase in temperature, from 300 °C to 500 °C, generated residual strain release and atomic diffusions, resulting in grain growth and a reduction in the band gap. The changes in UV and PL spectra predicted the growth kinetics involved

Design of back-contact interface of Cu(In,Ga)Se<sub>2</sub> solar cells by single-target magnetron sputtering

Thin-film solar cells provide an opportunity to reduce the cost of converting solar energy into electricity by replacing expensive and thick silicon wafers, which account for more than 50% of the total cost of photovoltaic (PV) modules. However, many thin-film solar cell materials result in low PV performance due to enhanced recombination through defect states. Cu(In,Ga)Se<sub>2</sub> (CIGS) is a promising thin-film solar cell material due to its direct tunable bandgap, high absorption coefficient, low effective electron and hole mass, and abundant constituent elements. Among them, magnetron sputtering or selenization technology is widely used to catch up with the development of preparing large-area CIGS thin-film solar cells because of its uniform film composition and simple process. However, the use of toxic gases such as H<sub>2</sub>Se and H<sub>2</sub>S and the difficulty in forming gradient bandgaps limit their development. In this work, the “V” Ga gradient classification of the absorbing layer of CIGS solar cells is realized by sputtering CuGaSe<sub>2</sub> (CGS) thin layers of different thickness values in the room temperature layer by sputtering and selenium-free methods of quaternary target sputtering. Firstly, the microstructure of the film is characterized by scanning electron microscope, X-ray diffraction, Raman and X-ray photoelectron spectroscopy, and when the CGS layer is located in the middle of the low-temperature layer, the grain size of the film is the largest, the crystallinity is the best, forming a “V-shaped” structure of CGI on the back of the absorbing layer. Subsequently, IV and external quantum efficiency (EQE) tests show that the optimized cell efficiency is as high as 15.04%, and the light response intensity is enhanced in the 300 －1200 nm band. Finally, the admittance spectrum(AS) test shows that the defect energy level of the solar cell changes from In<sub>Ga</sub> defect to <i>V</i><sub>Cu</sub> defect of lower energy level, and the defect density decreases from 7.04×10<sup>15</sup> cm<sup>–3</sup> to 5.51×10<sup>15</sup> cm<sup>–3</sup>. This is comparable to the recording efficiency of the current single-target magnetron sputtering CIGS solar cells, demonstrating good application prospects.

Deformation mechanisms in high entropy alloys: a minireview of short-range order effects.

The complex atomic scale structure of high entropy alloys presents new opportunities to expand the deformation theories of mechanical metallurgy. In this regard, solute-defect interactions have emerged as critical piece in elucidating the operation of deformation mechanisms. While notable progress has been made in understanding solute-defect interactions for random solute arrangements, recent interest in high entropy alloys with short-range order adds a new layer of structural complexity for which a cohesive picture has yet to emerge. To this end, this minireview synthesizes the current understanding of short-range order effects on defect behavior through an examination of the key recent literature. This analysis centers on the nanoscale metallurgy of deformation mechanisms, with the order-induced changes to the relevant defect energy landscapes serving as a touchstone for discussion. The topics reviewed include dislocation-mediated strengthening, twinning and phase transformation-based mechanisms, and vacancy-mediated processes. This minireview concludes with remarks on current challenges and opportunities for future efforts.

Simulation of displacement damage of InP induced by protons and α-particles in low Earth orbit

Indium phosphide (InP) material hasmany advantages, such as large band gap, high electron mobility, high photoelectric conversion efficiency, high temperature resistance, and radiation resistance, which is superior to silicon (Si) and gallium arsenide (GaAs). Meanwhile InP is widely used in optical communication, high-frequency millimeter waves, optoelectronic integrated circuits, satellite communication, space solar cells, and other fields. Radiation particles incident on InP device can generate displacement atoms inside the device through elastic processes. And these displacement atoms continue cascade collisions to generate lattice defects which are vacancies, interstitials, and clusters. These defects capture electrons-holes by defective energy levels in the energy band, and then resulting in a decrease in the life of minority carriers which is the reason of degradation of InP devices. The process of degradation of InP device, induced by lattice defects from ion-irradiation, is called displacement damage effect (DDE). The non-ionizing loss energy (NIEL) scaling is a useful method to predict the degradation of device caused by DDE of radiation particles. Many studies have shown that the NIEL is linearly related to the damage coefficient of InP device. Previous studies of radiation damage effect of InP device mainly focused on single-energy protons, electrons, and neutrons. Of the particles in low earth orbit (LEO),the vast majority of particles are protons, with a few being α particles and electrons, while the electron’s NIEL is too small and its DDE is negligible. The InP’s NIEL induced by proton and α energy in LEO has not been studied in detail. Therefore, this paper uses Monte Carlo software Geant4 to study the NIEL, damage energy distribution with depth, and annual total non-ionization loss energy generated by protons and α particles in LEO in 500/1000/5000 μm InP materials. The shielding of 150-μm-thick SiO<sub>2</sub> layer and 2.54-mm-thick Al layer from protons and α particles are used as InP solar cell and InP devices in spacecraft, respectively. It is found that the energy spectrum determines the non-ionizing damage energy <inline-formula><tex-math id="M1">\begin{document}$ {T}_{\text{dam}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231499_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231499_M1.png"/></alternatives></inline-formula> distribution, and then influences the NIEL value: the NIEL value increases with <inline-formula><tex-math id="M2">\begin{document}$ {T}_{\text{dam}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231499_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231499_M2.png"/></alternatives></inline-formula> increasing and thickness of InP material decreasing. And α NIEL is larger than proton’s, the single particle DDE of InP device, induced by α particles, should be concerned. The annual non-ionizing damage energy of proton accounts for 98%, which means that proton is the main factor degrading InP devices in LEO.

ELECTROPHYSICAL PROPERTIES OF A SOLAR CELL WITH NON-TRADITIONAL CONTACT STRUCTURES

Based on a number of experimental and patented works, the competitive efficiency of a solar cell with non-traditional contact structures is substantiated in detail. It is shown that the efficiency of a solar cell depends on the innovative choice of its contact materials (nano-sized crystalline lead chalcogenide and structureless non-crystalline silicon). The specific electro physical properties of lead chalcogenide and silicon are considered, providing a significant improvement in the converting properties of the solar cell. A specific mechanism for the formation of a contact field due to the participation of current carriers from localized defect energy states of the silicon band gap is presented. By solving the Poisson equation, the parameters of the contact field of the - nano-heterojunction were calculated.

Tailoring Broadband Nonlinear Optical Characteristics and Ultrafast Photocarrier Dynamics of Bi2O2S Nanosheets by Defect Engineering.

Low-dimensional bismuth oxychalcogenides have shown promising potential in optoelectronics due to their high stability, photoresponse, and carrier mobility. However, the relevant studies on deep understanding for Bi2O2S is quite limited. Here, comprehensive experimental and computational investigations are conducted in the regulated band structure, nonlinear optical (NLO) characteristics, and carrier dynamics of Bi2O2S nanosheets via defect engineering, taking O vacancy (OV) and substitutional Se doping as examples. As the OV continuously increased to ≈35%, the optical bandgaps progressively narrow from ≈1.21 to ≈0.81eV and NLO wavelengths are extended to near-infrared regions with enhanced saturable absorption. Simultaneously, the relaxation processes are effectively accelerated from tens of picoseconds to several picoseconds, as the generated defect energy levels can serve as both additional absorption cross-sections and fast relaxation channels supported by theoretical calculations. Furthermore, substitutional Se doping in Bi2O2S nanosheets also modulate their optical properties with the similar trends. As a proof-of-concept, passively mode-locked pulsed lasers in the ≈1.0µm based on the defect-rich samples (≈35% OV and ≈50% Se-doping) exhibit excellent performance. This work deepens the insight of defect functions on optical properties of Bi2O2S nanosheets and provides new avenues for designing advanced photonic devices based on low-dimensional bismuth oxychalcogenides.

Enhancing Photodetection Performance and Thermal Tolerance of CdS Thin Films through Cobalt (Co) Doping

A visible light photodetector is developed using cobalt (Co)‐doped cadmium sulfide (CdS) thin films that exhibits outstanding characteristics with a photocurrent of 284 μA, responsivity of 13.2 A W−1, an extraordinary external quantum efficiency (EQE) of 4550%, exceptional sensitivity (2.84 × 106%), and a rapid response time of 0.6 ms. These remarkable properties are most pronounced in 1 wt% Co‐doped CdS device and decrease with higher Co doping concentrations. This enhanced performance is attributed to the introduction of a defect energy band (DEB) near the CdS valence band, supported by UV‐Vis absorption spectra with a distinct feature at 744 nm. This DEB remains fully populated at room temperature and plays a vital role in responding to temperature variations. Our investigation reveals that 1 wt% Co‐doped CdS device exhibits significant (90%) thermal tolerance compared to pure CdS (10%) and higher Co doping concentrations (20%) in the temperature range of 27–110 °C. This improved thermal stability is attributed to the optimal Co doping concentration, striking a balance between thermal and photo‐excitation processes, thereby stabilizing the photocurrent. This research offers valuable insights into Co‐doped CdS thin films, promising robust and reliable photodetection devices, particularly suitable for applications with fluctuating temperatures.

Quantitative method to predict the energetics of helium-nanocavities interactions in metal systems based on electrophobic interaction

Energetics of helium-nanocavities interactions are crucial for unveiling underlying mechanisms of nanocavity evolution in nuclear materials. Nevertheless, it becomes intractable and even not feasible to obtain these energetics via atomic simulations with increasing nanocavity size and increasing helium content in nanocavities. Herein, a universal scaling law of helium-induced interaction energies in nanocavities in metal systems is proposed based on electrophobic interaction of helium. Based on this scaling law and ab-initio calculations, a predictive method for binding energies of helium and displacement defects to nanocavities of arbitrary sizes and with different helium/vacancy ratios is established for BCC iron as a representative and validated by atomic simulations. This predictive method reveals that the critical helium/vacancy ratio for helium-enhanced vacancy binding to nanocavities increases with increasing nanocavity size, and the helium/vacancy ratio giving the highest stability of nanocavities is about 1.6. The Ostwald ripening of nanocavities is delayed by helium to higher temperatures due to reduced vacancy de-trapping rates from nanocavities. The proposed scaling law can be generalized to many metal systems studied in the nuclear materials community. Being readily coupled into mesoscale models of irradiation damages, this predictive method facilitates clarifying helium role in cavity swelling of metallic nuclear materials.

Proton-Coupled Electron Transfer Involving Localized Electronic Defects on Solid Surfaces

Proton-coupled electron transfer (PCET) is a critical elementary step in many (photo)electrocatalytic transformations. PCET reactions on semiconducting metal oxide surfaces involve proton transfer that is charge compensated by electronic defects, such as electrons or holes. When highly localized as small polarons, these electronic defects are coupled with local bond distortions that accompany the excess or depleted charge. Using anatase TiO2 as a model system, I will describe recent first-principles modeling studies of interfacial PCET on metal oxide surfaces. The PCET reaction free energies involving the cleavage of O–H bonds on TiO2 surfaces varies widely depending on whether the charge-compensating electronic defects are conduction d-band electrons or valence p-band holes. Differences in PCET thermochemistry are accounted for using a Marcus theory framework based on defect energy levels and inner-sphere reorganization energies. The PCET rate constants associated with the cleavage of O–H bonds in the presence of a nitroxyl radical oxidant are calculated using vibronically nonadiabatic PCET theory, where both the transferring electron and proton are treated quantum mechanically. Input parameters to the rate constant expressions are calculated using hybrid periodic density functional theory calculations. These studies highlight the effects of local electronic defects on the PCET reactivity of semiconductor surfaces.

Thickness-dependent optical bandgap of WS2/glass thin films deposited PLD method and their optical limitations and nonlinear optical properties by using the CW laser beam(532 nm)

WS2 thin films were deposited on glass substrates (WS2/glass) using the pulsed laser deposition (PLD) method with thicknesses of 30 and 190 nm. The crystalline structure and elemental composition of the WS2 thin films were analyzed through X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to measure uniform, hexagonally cross-sectioned cones with smooth and even surfaces. Raman spectroscopy was utilized to assess the crystallinity and layer count in the WS2 thin films. Optical absorption, Tauc, and Urbach plots were employed to determine the optical bandgap energy (Eg) and defect energy Urbach (ED) of WS2 thin films with thicknesses of 30 nm and 190 nm. The 190 nm thick film exhibited an indirect bandgap transition with an energy value of 1.41 eV, whereas the 30 nm thin film showed a direct bandgap transition with an energy value of 1.98 eV. The defect energy Urbach was measured at 1.28 eV for the 30 nm WS2 film and 0.83 eV for the 190 nm film. Open aperture (OA) Z-scan analysis was conducted using a continuous-wave (CW) laser at 532 nm. The nonlinear absorption coefficient (β) was calculated for two different intensities, yielding values of 20.62 and 17.4 cmW for the 30 nm WS2 thin film and 13.75 and 13.35 cmW for the 190 nm film. The values of Imχ(3) and the figure of merit increased as the thin film size decreased for different sizes of WS2 films (30 nm and 190 nm). The optical limiting threshold and clamping point for the 30 nm WS2 thin film were found to be between 30–110 mW. It is evident that the higher β value for the WS2 thin film (30 nm) indicates a more effective limiting behavior.

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.