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A recent paper by L. Zheng [Phys. Plasmas 30, 042515 (2023)] presented a critical analysis of standard Lie-transform perturbation theory and suggested that its application to the problem of charged-particle motion in a magnetic field suffered from ordering inconsistencies. In the present Comment, we suggest that this criticism is unjustified and that standard Lie-transform perturbation theory does not need to be modified in its application to guiding-center theory. [ABSTRACT FROM AUTHOR]

Lattice distortion is considered to be one of the four core effects in a multicomponent high-entropy alloy. However, their effect is least understood from experiment and theoretical standpoints. The present investigation revealed a unique way to understand this effect by combining experiments with density functional theory (DFT) calculations. A small amount of Al and Si were carefully added to the whole-solute matrix of Cantor alloys. The different-sized atomic species introduces a huge lattice distortion in the matrix, leading to a simultaneous improvement in yield strength (YS), ultimate tensile strength (UTS), and percent elongation. An extensive DFT simulation indicates that a lattice distortion is prominent in an Al-containing alloy, whereas Si does not induce a lattice distortion. However, Si leads to severe interlayer lattice distortion, caused by the displacement of Si, during twinning. This leads to the improvement of YS, UTS, and ductility. Lattice distortion and its variants play significant effects on the mechanical properties of high-entropy alloys (HEAs) in terms of local lattice distortion, providing an uneven energy landscape for the movement of line defects or interlayer distortion. The inherent nature of local lattice distortion in HEAs leads to the wavy or tortuous dislocation, unlike a straight dislocation in conventional alloys. The movement of the wavy type of dislocation through a distorted or defective lattice requires large stress, resulting in a pronounced effect on solid solution strengthening. This local lattice distortion also dictates the degree of the interlayer distance distortion in the vicinity of atoms, leading to an increase or decrease in stable stacking fault energy that decides the deformation mode via slip or twinning. [ABSTRACT FROM AUTHOR]

Pyroelectric infrared detectors (PIRDs) have a number of advantages over other IR sensors, including room-temperature operation, wide wavelength sensitivity, and low cost, leading to their use in many applications and a market expected to reach U.S.$68 million by 2025. Physical models that can be used to accurately predict the performances of PIRDs of different types are reviewed in detail. All polar dielectrics exhibit the pyroelectric effect, so there are many materials potentially available for use in PIRDs. Traditionally, a range of "figures-of-merit" (FoMs) are employed to aid the selection of the best material to use in a given application. These FoMs, and their utility in determining how a given pyroelectric material will behave in a PIRD, are reviewed in the light of the physical models and the availability of dielectric data, which cover the frequency ranges of greatest interest for PIRDs (0.1–100 Hz). The properties of several pyroelectric materials are reviewed, and models are derived for their dielectric properties as functions of frequency. It is concluded, first, that the availability of full-frequency dielectric data is highly desirable if accurate predictions of device performance are to be obtained from the models and that second, the FoMs have practical utility in only very limited circumstances. Thus, they must be used with considerable care and circumspection. The circumstances under which each FoM is likely to give a good prediction for utility are discussed. The properties of some recently researched pyroelectric materials, including lead-containing single crystals in the Pb[(Mg⅓Nb⅔)xTi1−x]O3 system and Na½Bi½TiO3–K½Bi½TiO3 based lead-free crystals and ceramics, are reviewed in the light of this, and their properties and potential for device applications compared with the industry-standard material, LiTaO3. It is concluded that while there is potential for significant device performance improvements by using improved materials, especially with the PMN-PT-based materials, factors such as temperature stability, uniformity, and ease-of-processing are at least as important as device performance in determining material utility. The properties reported for the new lead-free materials do not, as yet, promise a performance likely to compete with LiTaO3 for mm-scale detectors, a material that is both readily available and lead-free. [ABSTRACT FROM AUTHOR]

By providing frequent, timely, and insightful reviews, these reviewers generously provide the highest levels of judgment and critical analysis to the authors, editors, and readers of I Biomicrofluidics i . The following topical experts served as reviewers for papers submitted to I Biomicrofluidics i during 2021. The Editors especially recognize Roy Beck, Wang Chaohui, Ian Foulds, Andrea Diaz Gaxiola, Arvind Gopinath, Robert Guy, Han Wei Hou, Xian Yeow Lee, Weihua Li, Shaohua Ma, Michael Mak, Louis Ong, Je-Kyun Park, Prabhakar Ranganathan, Amy Rowat, Shahrokh Sepehrirahnama, and Yi-Chung Tung. [Extracted from the article]

Aqueous alkali and multivalent metal-ion batteries are practically advantageous for large-scale energy storage because of intrinsic safety and environmental friendliness. Drawbacks, however, include low energy density and short life because of limited electrochemical stability windows (ESWs) of aqueous electrolytes and rapid degradation of electrode materials with high water activity. Despite significant research, including water-in-salt and electrolyte additive(s), directed to the electrolyte to extend ESWs and to boost electrode stability, the practical application remains limited because of the present high cost and generally unsatisfactory performance. Although alkali and multivalent metal ions can have different coordinating structures with solvents and anions, electrolyte design strategies share fundamental mechanisms in either extending ESWs or achieving a passivation layer on the electrode material(s). Future development of aqueous batteries, therefore, is dependent on a systematic understanding and analysis of electrolyte research. Here, we report for the first time a systematic review of the design and engineering of emerging water-based electrolytes for boosted aqueous rechargeable batteries (ARBs) performance. We present a comparative summary of electrochemical stability windows and electrode/electrolyte interphases for five (5) electrolyte types; appraise strategies and the resulting impact of electrolyte properties on electrode interfacial stability; analyze in situ generated electrode/electrolyte interphases; classify advantages and drawbacks of selected strategies; and provide a perspective on future developments in aqueous alkali and multivalent metal-ion batteries, together with methods for the study of both electrolyte and derived interphase(s). We conclude that (1) the design of electrolytes of high concentration and hybrid and eutectic solvents are practically promising for high energy density ARBs; (2) there is a need to improve design for longer cycling life of ARBs; (3) research addresses boosting ESW of the electrolyte; and (4) it increased the understanding of the electrode/electrolyte interface stability via new electrode/electrolyte interphase structures. This review will be of benefit in the practical design of electrolyte(s) for aqueous batteries for high performance and, therefore, of interest to researchers and manufacturers. [ABSTRACT FROM AUTHOR]

Micropropulsion systems are rapidly gaining attention from the small satellite community as they can increase the mission lifetime and allow the satellite to perform complex maneuvers and precise attitude control. These systems need to be fully operational with the low power available on satellites. Various thruster concepts based on vacuum arcs are currently under development, predominantly in the pulsed regime due to the power constraints on small spacecraft. Pulsed vacuum arc thrusters are capable of efficiently producing highly-ionized supersonic plasma at very low average power. This Perspective article provides a critical analysis and a review of various aspects of electric propulsion technology based on vacuum arcs. Furthermore, we give a personal assessment of the present status and provide an outlook on the field, including the growing role in small satellites such as CubeSats. Vacuum arc micropropulsion systems could play an important role in mitigating the problem of space debris. Such a system could be integrated with a satellite so that, at the end of its mission and using metal components as solid fuel, it will lower the satellite's orbit and accelerate reentrance into the atmosphere faster than by its natural decay rate. [ABSTRACT FROM AUTHOR]

Faddeeva–Voigt broadening (FVB) couples the physical characteristics of both Lorentzian and Gaussian profiles as a combined analytic function shaping the dielectric response. Accurate extraction of the Gaussian and Lorentzian broadening contents in line-shape analysis is essential for reliable optical characterization of semiconductors and dielectrics. By adding the Gaussian-broadening width to each Lorentzian width, we investigate how FVB affects critical-point (CP) analysis. We revisit a selection of earlier work based on classical Lorentz broadening in modulation spectroscopy and spectral ellipsometry. To generalize CP analysis, we derive the FVB's analytical representation in terms of fractional derivatives of the Faddeeva function and apply the twenty-pole Martin–Donoso–Zamudio approximation for its precise and efficient computation of the FVB of model dielectric functions and derivatives. We investigate the FVB of the electroreflectance line shape of HgCdTe for three-dimensional M0 transitions and of the photoreflectance line shape of InP excitonic E0 transitions. Furthermore, we explore how FVB affects the dielectric functions of three-dimensional excitonic and two-dimensional M0 transitions vs Tanguy's analytical two-dimensional exciton E1 and E1+Δ1 fits of GaAs to the second-order derivatives. We use the Akaike information criterion to quantitatively estimate the goodness of fit that statistically penalizes overfitting due to extraneous parameters. By consolidating both Gaussian and Lorentzian broadenings, the FVB significantly affects the CP analysis of modulation-spectroscopy line shapes and second-order derivatives of the dielectric function. [ABSTRACT FROM AUTHOR]

Electrolyte-gate transistors are a powerful platform for control of material properties, spanning semiconducting behavior, insulator-metal transitions, superconductivity, magnetism, optical properties, etc. When applied to magnetic materials, for example, electrolyte-gate devices are promising for magnetoionics, wherein voltage-driven ionic motion enables low-power control of magnetic order and properties. The mechanisms of electrolyte gating with ionic liquids and gels vary from predominantly electrostatic to entirely electrochemical, however, sometimes even in single material families, for reasons that remain unclear. In this Perspective, we compare literature ionic liquid and ion gel gating data on two rather different material classes—perovskite oxides and pyrite-structure sulfides—seeking to understand which material factors dictate the electrostatic vs electrochemical gate response. From these comparisons, we argue that the ambient-temperature anion vacancy diffusion coefficient (not the vacancy formation energy) is a critical factor controlling electrostatic vs electrochemical mechanisms in electrolyte gating of these materials. We, in fact, suggest that the diffusivity of lowest-formation-energy defects may often dictate the electrostatic vs electrochemical response in electrolyte-gated inorganic materials, thereby advancing a concrete hypothesis for further exploration in a broader range of materials. [ABSTRACT FROM AUTHOR]

We present a critical analysis of the popular fragment-orbital density-functional theory (FO-DFT) scheme for the calculation of electronic coupling values. We discuss the characteristics of different possible formulations or "flavors" of the scheme which differ by the number of electrons in the calculation of the fragments and the construction of the Hamiltonian. In addition to two previously described variants based on neutral fragments, we present a third version taking a different route to the approximate diabatic state by explicitly considering charged fragments. In applying these FO-DFT flavors to the two molecular test sets HAB7 (electron transfer) and HAB11 (hole transfer), we find that our new scheme gives improved electronic couplings for HAB7 (-6.2% decrease in mean relative signed error) and greatly improved electronic couplings for HAB11 (-15.3% decrease in mean relative signed error). A systematic investigation of the influence of exact exchange on the electronic coupling values shows that the use of hybrid functionals in FO-DFT calculations improves the electronic couplings, giving values close to or even better than more sophisticated constrained DFT calculations. Comparing the accuracy and computational cost of each variant, we devise simple rules to choose the best possible flavor depending on the task. For accuracy, our new scheme with chargedfragment calculations performs best, while numerically more efficient at reasonable accuracy is the variant with neutral fragments. [ABSTRACT FROM AUTHOR]

Half-Heusler alloys have been the focus of recent experimental research as emerging thermoelectric materials. Particular attention has been focused on the MNiSn (M=Ti, Zr, and Hf) alloys with substitutions made to reduce the lattice thermal conductivity and enhance the electrical transport properties. The effect of these substitutions on the relaxation time of phonon scattering in the material, and the impact on the lattice thermal conductivity, was investigated with a focus on modeling the experimental data. A modified Callaway model was used to describe experimental data, which were then compared to theoretical results predicted using phonon scattering by mass fluctuation and strain field models. The correlation between the coefficients obtained with experimental fits and theoretical models shows a predictable and systematic relationship between alloy composition and the thermal conductivity. In addition, the role of the normal (N) phonon-phonon scattering process is investigated following a recent theoretical study that indicated that the effect of N-process was underestimated in original Callaway's model. A comparison of the lattice thermal conductivity behavior using the phonon relaxation times in the original Callaway's model and the newly suggested theoretical model by Allen for the normal process is presented and discussed. [ABSTRACT FROM AUTHOR]

Using a simple empirical model based upon the bremsstrahlung isochromat spectroscopy of elemental Th, it is possible to explain the recent high energy resolution fluorescence detection measurements of UF4 (n = 2) and UCd11 (n = 3) as well as the new inverse photoelectron spectroscopy of Pu2O3 (n = 5), where n is the 5f occupation number. A critical issue in this analysis is the assumption that the Th 5f states are essentially empty, which will be confirmed both experimentally and computationally. Thus, for 5f systems, this simple model provides a unified and consistent picture of 5f unoccupied density of states in simple, localized systems, as the 5f occupation varies in the early part of the series, for n = 0, 2, 3, and 5. [ABSTRACT FROM AUTHOR]

The analysis of critical dimensions of nanostructured areas should ideally give both their size with nanometer resolution and the size distribution over a large area, two contradicting goals for most microscopic techniques. Here, we demonstrate that Mueller-matrix metrology is a fast and nondestructive technique able to identify deviations, as small as 1 to 2 nm, from the desired shape and the statistical distribution of sizes on a potentially unlimited area. Tiny shape deviations are accessible from Mueller-matrix measurements over a complete azimuthal rotation after the subsequent differential decomposition of the matrices and elucidated from small anisotropies. The size distribution is hidden in the depolarization and is extracted by comparing the simulated and measured sum-decomposed Mueller matrices. This study especially demonstrates that depolarization concealed in measured Mueller matrices contains valuable information about the sample. [ABSTRACT FROM AUTHOR]

We present a critical analysis of available experimental and theoretical cross section data for positron scattering from atomic systems. From this analysis, we present (where data are available) recommended cross sections for total scattering, positronium formation, inelastic scattering, and direct ionization processes. A complete bibliography of available measurement and theory is also presented. [ABSTRACT FROM AUTHOR]