bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of coverage, water, and defects on Catechol/TiO2 interface
Authors: Wei Min , Jin Fan , Liang Chenggong , Zhang Lijuan , Qiao Shizhu , Ma Yuchen
Published: July 2022

Catechol adsorbed on TiO2 is one of the simplest models to explore the relevant properties of dye-sensitized solar cells. However, the effects of water and defects on the electronic levels and the excitonic properties of the catechol/TiO2 interface have been rarely explored. Here, we investigate four catechol/TiO2 interfaces aiming to study the influence of coverage, water, and defects on the electronic levels and the excitonic properties of the catechol/TiO2 interface through the first-principles many-body Green’s function theory. We find that the adsorption of catechol on the rutile (110) surface increases the energies of both the TiO2 valence band maximum and conduction band minimum by approximately 0.7 eV. The increasing coverage and the presence of water can reduce the optical absorption of charge-transfer excitons with maximum oscillator strength. Regarding the reduced hydroxylated TiO2 substrate, the conduction band minimum decreases greatly, resulting in a sub-bandgap of 2.51 eV. The exciton distributions in the four investigated interfaces can spread across several unit cells, especially for the hydroxylated TiO2 substrate. Although the hydroxylated TiO2 substrate leads to a lower open-circuit voltage, it may increase the separation between photogenerated electrons and holes and may therefore be beneficial for improving the photovoltaic efficiency by controlling its concentration. Our results may provide guidance for the design of highly efficient solar cells in future.
In-situ measurements of reconstructed anatase TiO2(001) surface by variable-temperature STM
Authors: Liu Jianyi , Ma Xiaochuan , Li Xintong , Cheng Zhengwang , Cui Xuefeng , Wang Bing
Published: July 2022

The catalytic performance of metal oxide surface mainly depends on its atomic surface structure, which usually changes under various treatment conditions and during catalytic reactions. Therefore, it is quite important to acquire the atomic geometries of the surfaces under different treatments for further understanding the catalytic mechanisms in the surfaces with complicated reconstructions. Here, we report the investigation on the evolution of surface geometries of the Ar+-ion-sputtered anatase TiO2(001) films followed by heating treatments at various temperatures, characterized using variable-temperature scanning tunneling microscopy. Our experimental results reveal the different surface morphologies at different heating temperatures. During the heating treatment, the migrations of O atoms from the bulk to the surface of TiO2(001) play an important role in the reoxidation of the Ti2+ and Ti3+ states for the formation of (1×4) reconstruction. The atomic-resolution images of the ridges show asymmetric features, which well support the fully oxidized structural model of the reconstructed TiO2(001)-(1×4) surface.
Reaction mechanism of one-step conversion of ethanol to 1,3-butadiene over Zn-Y/BEA and superior catalysts screening
Authors: Dang Shu-Xuan , Liu Han-Xuan , Ban Tao , Gao Xin , Huang Zheng-Qing , Yang Dong-Yuan , Chang Chun-Ran
Published: July 2022

The one-step conversion of ethanol to 1,3-butadiene has achieved a breakthrough with the development of beta zeolite supported dual metal catalysts. However, the reaction mechanism from ethanol to butadiene is complex and has not yet been fully elucidated, and no catalyst screening effort has been done based on central metal atoms. In this work, density functional theory (DFT) calculations were employed to study the mechanism of one-step conversion of ethanol to butadiene over Zn-Y/BEA catalyst. The results show that ethanol dehydrogenation prefers to proceed on Zn site with a reaction energy of 0.77 eV in the rate-determining step, and the aldol condensation to produce butadiene prefers to proceed on Y site with a reaction energy of 0.69 eV in the rate-determining step. Based on the mechanism revealed, six elements were selected to replace Y for screening superior combination of Zn-M/BEA (M=Sn, Nb, Ta, Hf, Zr, Ti; BEA: beta polymorph A) for this reaction. As a result, Zn-Y/BEA (0.69 eV) is proven to be the most preferring catalyst compared with the other six ones, and Zn-Zr/BEA (0.85 eV), Zn-Ti/BEA (0.87 eV), and Zn-Sn/BEA (0.93 eV) can be potential candidates for the conversion of ethanol to butadiene. This work not only provides mechanistic insights into one-step catalytic conversion of ethanol to butadiene over Zn-Y/BEA catalyst but also offers more promising catalyst candidates for this reaction.
Mixed quantum classical reaction rates based on the phase space formulation of the hierarchical equations of motion
Authors: Xing Tao , Li Tianchu , Liu Yanying , Shi Qiang
Published: July 2022

In a previous work [J. Chem. Phys. 140, 174105 (2014)], we have shown that a mixed quantum classical (MQC) rate theory can be derived to investigate the quantum tunneling effects in the proton transfer reactions. However, the method is based on the high temperature approximation of the hierarchical equation of motion (HEOM) with the Debye-Drude spectral density, and results in a multistate Zusman type of equation. We now extend this theory to include quantum effects of the bath degrees of freedom. By writing the full HEOM into a multidimensional partial differential equation in phase space, we can define a new reaction coordinate, and the previous method can be generalized to the full quantum regime. The validity of the new method is demonstrated by using numerical examples, including the spin-Boson model, and the double well model for proton transfer reaction. The new method is found to resolve some key problems of the previous theory based on high temperature approximation, including possible numerical instability in long time simulation and wrong rate constant at low temperatures.
Progress in in situ x-ray imaging of welding process
Authors: Zhang Xiaolin , Tang Zijue , Wu Yi , Devoino Oleg , Wang Haowei , Wang Hongze
Published: July 2022

Welding has been widely used in industry for hundreds of years, and pursuing higher weld quality requires a better understanding of the welding process. The x-ray imaging technique is a powerful tool to in situ observe the inner characteristics of the melt pool in the welding process. Here, current progress in in situ x-ray imaging of the welding process is concluded, including the experiments based on the laboratory-based single x-ray imaging system, the laboratory-based double x-ray imaging system, and the synchrotron radiation tomography system. The corresponding experimental results with the in situ x-ray imaging technique about the formation and evolution of the keyhole, melt pool, pore, solidification crack, etc., have been introduced. A new understanding of welding based on the current progress in in situ x-ray imaging of additive manufacturing is concluded. In addition, the future development trend of applying x-ray imaging technology in the field of monitoring the welding process is proposed.
Restriction of Laplace operator on one-forms: From Rn+2 and Rn+1 ambient spaces to embedded (A)dSn submanifolds
Authors: Huguet E. , Queva J. , Renaud J.
Published: July 2022

The Laplace–de Rham operator acting on a one-form a: □a in Rn+2 or Rn+1 spaces is restricted to n-dimensional pseudo-spheres. This includes, in particular, the n-dimensional de Sitter and anti-de Sitter space-times. The restriction is designed to extract the corresponding n-dimensional Laplace–de Rham operator acting on the corresponding n-dimensional one-form on pseudo-spheres. Explicit formulas relating these two operators are given in each situation. The converse problem of extending an n-dimensional operator composed of the sum of the Laplace–de Rham operator and additional terms to the Laplace–de Rham operator on ambient spaces is also studied. We show that for any additional term, this operator on the embedded space is the restriction of the Laplace–de Rham operator on the embedding space. These results are translated to the Laplace–Beltrami operator thanks to the Weitzenböck formula, for which a proof is also given.
Additive eigenvectors as optimal reaction coordinates, conditioned trajectories, and time-reversible description of stochastic processes
Authors: Krivov Sergei V.
Published: July 2022

A fundamental way to analyze complex multidimensional stochastic dynamics is to describe it as diffusion on a free energy landscape—free energy as a function of reaction coordinates (RCs). For such a description to be quantitatively accurate, the RC should be chosen in an optimal way. The committor function is a primary example of an optimal RC for the description of equilibrium reaction dynamics between two states. Here, additive eigenvectors (addevs) are considered as optimal RCs to address the limitations of the committor. An addev master equation for a Markov chain is derived. A stationary solution of the equation describes a sub-ensemble of trajectories conditioned on having the same optimal RC for the forward and time-reversed dynamics in the sub-ensemble. A collection of such sub-ensembles of trajectories, called stochastic eigenmodes, can be used to describe/approximate the stochastic dynamics. A non-stationary solution describes the evolution of the probability distribution. However, in contrast to the standard master equation, it provides a time-reversible description of stochastic dynamics. It can be integrated forward and backward in time. The developed framework is illustrated on two model systems—unidirectional random walk and diffusion.
Enhancement of radiation detection performance with reduction of EH6/7 deep levels in n-type 4H–SiC through thermal oxidation
Authors: Karadavut OmerFaruk , Chaudhuri Sandeep K. , Kleppinger Joshua W. , Nag Ritwik , Mandal Krishna C.
Published: July 2022

We report the effect of EH6/7 electron trap centers alone on the performance of high-resolution radiation detectors fabricated on n-type 4H–SiC epitaxial layers. A Schottky barrier detector (SBD) and a metal-oxide-semiconductor (MOS) capacitor detector fabricated using two sister samples derived from the same 50 μm 4H–SiC parent wafer exhibited widely different energy resolutions of 0.4% and 0.9% for 5486 keV alpha particles. An equivalent noise charge model analysis ruled out the effect of the detector capacitance and the leakage current on the resolution of the detectors. Deep level transient spectroscopic studies revealed the presence of two trapping centers in each detector within the temperature scan range 240–800 K. The Z1/2 center, a potential electron trap, was detected in both the detectors in equal concentration, which suggested that the observed difference in the energy resolution is due to the presence of the other defect, the EH6/7 center, in the SBD. The capture cross section of the EH6/7 center was calculated to be three orders of magnitude higher than the second defect [a carbon antisite vacancy (CAV) center] observed in the MOS detector with an activation energy of 1.10 eV, which accounted for the enhanced electronic trapping in the SBD leading to its poor energy resolution. It has been proposed that the EH6/7 centers in the SBD have likely been reconfigured to CAV pairs during the thermal growth of the silicon dioxide layer in the MOS detector. The proposed formation mechanism of CAV, a stable qubit state for quantum information processing, addresses the outstanding questions related to the role of defect dynamics in their formation.
Vibro-impact energy harvester for low frequency vibration enhanced by acoustic black hole
Authors: Zhang Liufeng , Tang Xiao , Qin Zhaoye , Chu Fulei
Published: July 2022

In this Letter, we propose an enhanced vibro-impact energy harvester using acoustic black holes (ABHs) for scavenging low-frequency vibration energy. The energy harvester involves two beams: a relatively rigid piezoelectric generating beam with ABH profile and a flexible driving beam with a tip mass mounted at the end. The tip mass and the generating beam collide repeatedly under low-frequency excitations. Experimental studies are conducted to investigate the output performance of the energy harvester by comparing the output power and voltage of generating beams with different tailored ends. Finite element analysis is also carried out to evaluate the influence of electrode number of the piezoelectric sheet attached to the ABH beam on the output performance of the energy harvester. It is shown that the impacts between the tip mass and generating beam are capable of transferring vibration energy from the low-frequency band to high-frequency band, where ABH gets a desirable energy focalization effect to improve the output performance of the energy harvester. The energy harvester achieves the best output performance when its electrode is divided into two parts with the excellent power of 0.7 mW at the low frequency range from 5 to 13 Hz.
A second order upper bound on the ground state energy of a Bose gas beyond the Gross–Pitaevskii regime
Authors: Basti Giulia
Published: July 2022

We consider a system of N bosons in a unitary box in the grand-canonical setting interacting through a potential with the scattering length scaling as N−1+κ, κ ∈ (0, 2/3). This regimes interpolate between the Gross–Pitaevskii regime (κ = 0) and the thermodynamic limit (κ = 2/3). In the work of Basti et al. [Forum Math., Sigma 9, E74 (2021)], as an intermediate step to prove an upper bound in agreement with the Lee–Huang–Yang formula in the thermodynamic limit, a second order upper bound on the ground state energy for κ < 5/9 was obtained. In this paper, thanks to a more careful analysis of the error terms, we extend the mentioned result to κ < 7/12.
Viscoelastic effects of immiscible liquid–liquid displacement in microchannels with bends
Authors: Hue Seng Hoe , Chagot Loïc , Angeli Panagiota
Published: July 2022

The displacement flow of an organic Newtonian fluid by a pure viscoelastic aqueous solution is experimentally investigated inside a circular microchannel of 200 μm. Displacement is commonly encountered in many industrial applications, from cleaning and decontamination to enhanced oil recovery. In this study, a pure viscoelastic fluid with no shear-thinning properties (known as Boger fluid) made up of polyethylene oxide, polyethylene glycol, and zinc chloride is used to displace an immiscible organic liquid (silicone oil). The results were compared against those from displacement with a Newtonian fluid of similar density and viscosity as the viscoelastic one. High-speed imaging is used to track both the residual film thickness of the organic phase and the interface deformations during displacement. It is found that the Boger fluid displacing phase produces a thinner displaced phase film compared to the Newtonian fluid, particularly at high capillary numbers. A correlation is proposed for the film thickness, which includes the Weissenberg number for the viscoelastic case. After the displacement front, the interface becomes unstable with two modes of instability identified. In the case of the Boger fluid, the two modes of instability are core shifting, which is also present in the Newtonian case, and a periodic instability from the elastic stresses during displacement. Additionally, the shape of the interfacial instabilities switches freely from asymmetric to axisymmetric ones throughout the flow. The frequency of the periodic instabilities increases with the displacing phase flow rate. It was also found that microchannel bends downstream of the observation point affect the shape and frequency of the instabilities.
Fröhlich electron–phonon interaction Hamiltonian and potential distribution of a polar optical phonon mode in wurtzite nitride triangular nanowires
Authors: Zhang Li , Shi Jun-Jie , Wang Qi
Published: July 2022

Polar optical phonon modes of wurtzite triangular nanowires (NWs) with three different cross sections, including the hemi-equilateral triangle (HET), the isosceles right triangle (IRT), and the equilateral triangle (ET), are deduced and analyzed using the dielectric continuum model. The exact and analytical phonon states of exactly confined (EC) modes in nitride NWs with HET, IRT, and ET cross sections are derived. The characteristic frequency of EC phonon modes in the triangular nitride NW systems is specified. Fröhlich electron–phonon interaction Hamiltonians in wurtzite NWs with three types of triangular cross sections are obtained. It is found from the numerical results that, among the three types of GaN NWs, the electron–phonon coupling of EC modes in NWs with an HET cross section is the weakest one, that in NWs with an ET cross section is the strongest one, and that in NWs with an IRT cross section is in the middle. The electrostatic potentials of EC modes in HET NWs are neither symmetric nor antisymmetric. The potential functions of EC modes in the ET NW structures have one (three) symmetric axis (axes) as the quantum numbers p and q take fractions (integers). The potential functions of EC modes in IRT NWs behave either symmetrically or anti-symmetrically, which are closely dependent on the parities of the quantum numbers p and q. With the increase of order-number of EC modes, the electron–phonon coupling becomes weaker and weaker. This reveals that cross-sectional morphology of quantum structures has an important influence on the symmetries of phonon modes and electron–phonon coupling strengths in low-dimensional quantum systems.
Study of a novel conservative chaotic system with special initial offset boosting behaviors
Authors: Leng Xiangxin , Tian Bowen , Zhang Limeng , Du Baoxiang
Published: July 2022

Conservative systems are increasingly being studied, while little research on fractional-order conservative systems has been reported. In this paper, a novel five-dimensional conservative chaotic system is proposed and solved in a fractional-order form using the Adomian decomposition method. This system is dissipative in the phase volume, but the sum of all Lyapunov exponents is zero. During the exploration, some special dynamical behaviors are analyzed in detail by using phase diagrams, bifurcation diagrams, Lyapunov exponential spectra, timing diagrams, and so on. After extensive simulation, several rare dynamical behaviors, including completely homogeneous, homogeneous, and heterogeneous initial offset boosting behaviors, are revealed. Among them, the initial offset boosting behaviors with identical phase trajectory structures have not been reported before, and the previously proposed homogeneous phase trajectories are locally different. By comparing with the integer-order system, two influence factors that affect the system to produce completely homogeneous and heterogeneous conservative flows are discovered. Eventually, the circuit is built on the digital signal processing (DSP) platform to demonstrate the physical realizability of the system. The experimental results are shown by the oscilloscope and agree with the theoretical analysis.
A new leakage detection method of molten salt tank and its experimental verification and optimization
Authors: Zuo Yuhang , Huang Zhonghua , Zhao Hui , Zhang Mingrui , Cheng Fangzheng , Shi Hua , Zhou Hao
Published: July 2022

Molten salt tank leak detection technology is essential for the timely detection and handling of leaks. Current common thermocouple leak detection technology cannot meet the demand, and more efficient leak detection technology is urgently needed. In this paper, a molten salt tank leakage detection circuit based on the conductivity of high-temperature molten salt is proposed for the first time. Its feasibility is verified by the experimental results of a lab-scale tank foundation experimental system, and a parametric analysis is carried out to optimize the circuit layout. The results show that when molten salt leaks to the measurement point of the circuit, the voltage of the constant resistor in the circuit first rises rapidly, then drops rapidly, and finally, reaches a steady value. The vertical spacing, arrangement depth, and operating temperature significantly influence the detection effect. To ensure the rapid and continuous detection of molten salt tank leakage, the vertical spacing should be less than 50 mm. The arrangement depth should be as close as possible to the bottom of the molten salt tank, preferably within 150 mm. The decrease in the operating temperature significantly deteriorates the continuous detection effect of the circuit. When the detection circuit is used in the cold molten salt tank of concentrating solar power plants, timely circuit detection signal processing and prompt mechanisms are required to ensure that the leakage accident is not missed.
Random-resistor network modeling of resistance hysteresis of vanadium dioxide thin films
Authors: Gu M. J. , Lin S. , Xu X. F. , Wang C. R. , Wu B. H. , Cao J. C.
Published: July 2022

The resistance hysteresis of vanadium dioxide (VO2) is a key feature in revealing mechanisms of a phase transition as well as emerging applications. In this study, a dynamical model based on random-resistor networks is developed to simulate the transport properties of VO2 thin films. The reversible metal–insulator phase transition of each microscopic domain is captured by a modified Landau-type functional. The proposed model enables analysis of not only the formation of conducting filaments driven by an electric field, but also the thermal-driving reversal curves of resistance hysteresis. It is shown that the appearance of a hysteresis loop as well as the aggregation of metallic domains can be tuned via the interactions of each domain with its neighbors and the substrate. The interaction effects are vital for the persistence of metallic domains, which can re-trigger the insulating-to-metallic transition by a subthreshold voltage bias with the delay time much longer than the transition switching time. These results are in agreement with experimental observations and can be helpful in developing VO2-based key components ranging from infrared bolometers to the volatile resistive switches for neuromorphic computing.
Observation of bandgap closing in SrxBa1−xBiO3 films: Evidence toward topological order in BaBiO3
Authors: Vesto Riley , Choi Hyungsoo , Kim Kyekyoon
Published: July 2022

Sr x Ba 1 − x BiO 3 (0≤x<0.5) films were fabricated from solution-phase precursors using flow-limited field-injection electrostatic spraying to investigate the predicted topological properties of BaBiO3, an oxide perovskite. The films were analyzed via x-ray diffraction, optical conductivity, and Raman spectroscopy. The bandgaps measured by optical absorption spectroscopy were in line with the predicted value of SrxBa1−xBiO3 for x<0.25, decreasing with an increase in x to reach zero at x=0.348. This suggests that BaBiO3 may have topological order and that, upon appropriate doping, it may be used as a topological insulator or superconductor in quantum-computing devices. This work may open up new avenues toward engineering of topological insulators with precise and reproducible control of stoichiometry, obviating extreme deposition temperatures or vacuum processing.
Soft-mode-phonon-mediated insulator–superconductor transition in doped two-dimensional topological insulator RuC
Authors: Wen Zhiyuan , Li Jiaheng , Wang Ziqiang , Xu Yong , Zhu Jing
Published: July 2022

Recently, the search of superconducting materials with topological states has attracted extensive interest due to their exotic properties. By using first-principles calculations, we predict that RuC monolayer is a two-dimensional topological insulator (TI) and shows a TI–superconductor transition under electron doping, leading to a superconducting transition temperature Tc of 1.4 K. Further analysis reveals that the emergence of superconductivity in RuC depends critically on the existence of flatband optical phonons as well as the appearance of multiple electron-pockets and phonon mode softening induced by doping. Moreover, we find that Li-intercalated RuC (LiRuC) is a thermal dynamically stable, superconducting material with a high Tc of 9.8 K, benefitting from the strong electron–phonon coupling. Many other superconductors with flat phonon bands are also predicted via elemental substitution in LiRuC. Our results will broaden the research interest in exploring more superconductors and modulating their physical properties through flat phonon bands.
Photoluminescent Bragg curves in lithium fluoride thin films on silicon substrates irradiated with a 35 MeV proton beam
Authors: Nichelatti E. , Nigro V. , Piccinini M. , Vincenti M. A. , Ampollini A. , Picardi L. , Ronsivalle C. , Montereali R. M.
Published: July 2022

Proton irradiation of lithium fluoride (LiF) crystals and thin films causes the formation of electronic defects, known as color centers, in the crystal lattice, some of which show photoluminescence in the visible range under blue-light excitation. With a suitable irradiation geometry, the energy density that protons deposit in the material can be recorded as a spatial distribution of these light-emitting color centers, from which a luminous replica of the proton Bragg curve can be thereafter extracted and analyzed in a fluorescence microscope. In this paper, the cases of two LiF thin films deposited on silicon substrates and of a LiF crystal, all of them transversally irradiated with a nominal 35 MeV proton beam, are considered. A comparison of the measured photoluminescent Bragg curves with Monte Carlo simulations demonstrates (i) that the Bragg peaks in the films are located at the very same positions that would be expected in the underlying silicon substrates rather than in LiF and (ii) that an even small grazing angle of the impinging proton beam is able to significantly modify the shape of the Bragg curve in the films. Both of these findings are ascribed to the effects of multiple Coulomb scattering in both the film and the substrate. The coincidence of the Bragg peak positions with those expected in the silicon substrates and the possibility of visualizing such peaks in the Bragg curves stored as latent fluorescence images in the LiF films allow one to regard them as information transducers for proton beam diagnostics and dosimetry.
Large-area total-thickness imaging and Burgers vector analysis of dislocations in
β
-Ga2O3 using bright-field x-ray topography based on anomalous transmission
Authors: Yao Yongzhao , Tsusaka Yoshiyuki , Sasaki Kohei , Kuramata Akito , Sugawara Yoshihiro , Ishikawa Yukari
Published: July 2022

Using bright-field x-ray topography based on anomalous transmission (AT), we have demonstrated the first large-area total-thickness imaging of dislocations in β-Ga2O3 at the substrate scale. The dislocation images were acquired from the entire 10 mm × 15 mm × 680 μm (001)-oriented substrate prepared by edge-defined film-fed growth (EFG) by stitching together hundreds of topographic images, each recorded with the forward-diffracted beam in the Laue geometry for g = 020, 0–20, 022, and 400, under the conditions in which AT occurred. Dislocations distributed over the entire crystal volume were imaged as long as their Burgers vectors (b) were not orthogonal to the g-vectors. The results of the g·b analysis of the dislocation contrasts clearly revealed three major dislocation types that were numerically dominant in the EFG crystal: (i) b-axis screw-type dislocations with b∥ξ∥[010] (ξ is the unit vector of line direction), (ii) b-axis edge-type dislocations with b∥[001] and ξ∥[010], and (iii) curved mixed-type dislocations lying on the (001) planes with b∥[010]. Based on their b- and ξ-vectors, types (i) and (ii) were attributed to dislocations that propagated during EFG pulling up along the [010] direction, while type (iii) was attributed to dislocations generated through glide in the [010](001) slip system under stress. The extent to which AT can manifest itself is explained by using the effective absorption coefficient calculated for the above g-vectors based on dynamical x-ray diffraction theory.
Orbital pair selection for relative energies in the domain-based local pair natural orbital coupled-cluster method
Authors: Bensberg Moritz , Neugebauer Johannes
Published: July 2022

For the accurate computation of relative energies, domain-based local pair natural orbital coupled-cluster [DLPNO-CCSD(T0)] has become increasingly popular. Even though DLPNO-CCSD(T0) shows a formally linear scaling of the computational effort with the system size, accurate predictions of relative energies remain costly. Therefore, multi-level approaches are attractive that focus the available computational resources on a minor part of the molecular system, e.g., a reaction center, where changes in the correlation energy are expected to be the largest. We present a pair-selected multi-level DLPNO-CCSD(T0) ansatz that automatically partitions the orbital pairs according to their contribution to the overall correlation energy change in a chemical reaction. To this end, the localized orbitals are mapped between structures in the reaction; all pair energies are approximated through computationally efficient semi-canonical second-order Møller–Plesser perturbation theory, and the orbital pairs for which the pair energies change significantly are identified. This multi-level approach is significantly more robust than our previously suggested, orbital selection-based multi-level DLPNO-CCSD(T0) ansatz [M. Bensberg and J. Neugebauer, J. Chem. Phys. 155, 224102 (2021)] for reactions showing only small changes in the occupied orbitals. At the same time, it is even more efficient without added input complexity or accuracy loss compared to the full DLPNO-CCSD(T0) calculation. We demonstrate the accuracy of the multi-level approach for a total of 128 chemical reactions and potential energy curves of weakly interacting complexes from the S66x8 benchmark set.
Continental islands off the Pacific Coast of the Mexican state of Jalisco hold complementary plant conservation value
Authors: Soria-González Victor Hugo , Benítez-Malvido Julieta , Suazo-Ortuño Ireri , Martínez Cruz Juan , Siliceo-Cantero Héctor Hugo
Published: July 2022

Context Continental islands are important conservation targets because of their ecological singularities. In the Mexican Pacific, the Chamela Bay Islands Sanctuary in the state of Jalisco is little or not studied at all in terms of biodiversity. Aims The aim of this study is to contribute to the management plan of the sanctuary by presenting a detailed analysis of native vegetation surveys of three islands of the sanctuary. Methods We used quadrats and treks to record and compare plant diversity, species richness, and structure of woody and cacti vegetation of the islands of Cocinas, La Pajarera, and San Agustín. Key results There are 42 woody and seven cacti species on the three islands (Cocinas 28, La Pajarera 17, San Agustín 30), which represent 9% and 42% of the woody and cacti species recorded regionally, respectively. The islands harbour 20 endemic Mexican species (regionally, 8.6% of woody and 30% of cacti species) and four species in some threatened category (regionally, 0.4%). Plant species richness and vegetation structure differ among the three islands, which shared only seven species. Conclusions The richness and abundance of woody and cacti species on the three islands (total area: 55.5 ha) that include Mexican endemic and threatened species emphasise the importance of protecting the whole islands. Implications The islands need a more active vigilance to avoid induced fires and vegetation removal. Our results point out these factors as the major threats for the islands’ conservation.
Solvent selection criteria for temperature-resilient lithium–sulfur batteries
Authors: Cai Guorui , Holoubek John , Li Mingqian , Gao Hongpeng , Yin Yijie , Yu Sicen , Liu Haodong , Pascal Tod A. , Liu Ping , Chen Zheng
Published: July 2022

All-climate temperature operation capability and increased energy density have been recognized as two crucial targets, but they are rarely achieved together in rechargeable lithium (Li) batteries. Herein, we demonstrate an electrolyte system by using monodentate dibutyl ether with both low melting and high boiling points as the sole solvent. Its weak solvation endows an aggregate solvation structure and low solubility toward polysulfide species in a relatively low electrolyte concentration (2 mol L
−1
). These features were found to be vital in avoiding dendrite growth and enabling Li metal Coulombic efficiencies of 99.0%, 98.2%, and 98.7% at 23 °C, −40 °C, and 50 °C, respectively. Pouch cells employing thin Li metal (50 μm) and high-loading sulfurized polyacrylonitrile (3.3 mAh cm
−2
) cathodes (negative-to-positive capacity ratio = 2) output 87.5% and 115.9% of their room temperature capacity at −40 °C and 50 °C, respectively. This work provides solvent-based design criteria for a wide temperature range Li-sulfur pouch cells.
Impact of warming on aquatic body sizes explained by metabolic scaling from microbes to macrofauna
Authors: Deutsch Curtis , Penn Justin L. , Verberk Wilco C. E. P. , Inomura Keisuke , Endress Martin-Georg , Payne Jonathan L.
Published: July 2022

Rising temperatures are associated with reduced body size in many marine species, but the biological cause and generality of the phenomenon is debated. We derive a predictive model for body size responses to temperature and oxygen (O
2
) changes based on thermal and geometric constraints on organismal O
2
supply and demand across the size spectrum. The model reproduces three key aspects of the observed patterns of intergenerational size reductions measured in laboratory warming experiments of diverse aquatic ectotherms (i.e., the “temperature-size rule” [TSR]). First, the interspecific mean and variability of the TSR is predicted from species’ temperature sensitivities of hypoxia tolerance, whose nonlinearity with temperature also explains the second TSR pattern—its amplification as temperatures rise. Third, as body size increases across the tree of life, the impact of growth on O
2
demand declines while its benefit to O
2
supply rises, decreasing the size dependence of hypoxia tolerance and requiring larger animals to contract by a larger fraction to compensate for a thermally driven rise in metabolism. Together our results support O
2
limitation as the mechanism underlying the TSR, and they provide a physiological basis for projecting ectotherm body size responses to climate change from microbes to macrofauna. For small species unable to rapidly migrate or evolve greater hypoxia tolerance, ocean warming and O
2
loss in this century are projected to induce >20% reductions in body mass. Size reductions at higher trophic levels could be even stronger and more variable, compounding the direct impact of human harvesting on size-structured ocean food webs.
Using a generative model of affect to characterize affective variability and its response to treatment in bipolar disorder
Authors: Pulcu Erdem , Saunders Kate E. A. , Harmer Catherine J. , Harrison Paul J. , Goodwin Guy M. , Geddes John R. , Browning Michael
Published: July 2022

The affective variability of bipolar disorder (BD) is thought to qualitatively differ from that of borderline personality disorder (BPD), with changes in affect persisting longer in BD. However, quantitative studies have not been able to confirm this distinction. It has therefore not been possible to accurately quantify how treatments like lithium influence affective variability in BD. We assessed the affective variability associated with BD and BPD as well as the effect of lithium using a computational model that defines two subtypes of variability: affective changes that persist (volatility) and changes that do not (noise). We hypothesized that affective volatility would be raised in the BD group, noise would be raised in the BPD group, and that lithium would impact affective volatility. Daily affect ratings were prospectively collected for up to 3 y from patients with BD or BPD and nonclinical controls. In a separate experimental medicine study, patients with BD were randomized to receive lithium or placebo, with affect ratings collected from week −2 to +4. We found a diagnostically specific pattern of affective variability. Affective volatility was raised in patients with BD, whereas affective noise was raised in patients with BPD. Rather than suppressing affective variability, lithium increased the volatility of positive affect in both studies. These results provide a quantitative measure of the affective variability associated with BD and BPD. They suggest a mechanism of action for lithium, whereby periods of persistently low or high affect are avoided by increasing the volatility of affective responses.
Geometric Upper Critical Dimensions of the Ising Model
Authors: Fang Sheng , Zhou Zongzheng , Deng Youjin
Published: July 2022

The upper critical dimension of the Ising model is known to be d
c = 4, above which critical behavior is regarded to be trivial. We hereby argue from extensive simulations that, in the random-cluster representation, the Ising model simultaneously exhibits two upper critical dimensions at (d
c = 4, d
p = 6), and critical clusters for d ≥ d
p, except the largest one, are governed by exponents from percolation universality. We predict a rich variety of geometric properties and then provide strong evidence in dimensions from 4 to 7 and on complete graphs. Our findings significantly advance the understanding of the Ising model, which is a fundamental system in many branches of physics.
Range-relaxed strategy applied to the Levenberg–Marquardt method with uniformly convex penalization term in Banach spaces
Authors: Margotti Fábio , Hafemann Eduardo
Published: July 2022

In this paper we propose the employment of the so-called range-relaxed criteria Boiger et al (2020 IMA J. Numer. Anal.
40 606–627) for choosing the regularization parameters (or equivalently, the Lagrange multipliers) of the Levenberg–Marquardt method for solving nonlinear ill-posed problems in Banach spaces. The proposed algorithm employs the Bregman distance induced by a uniformly convex functional and allows the use of a penalization generated from the total variation semi-norm. We present a geometrical interpretation of the method and deliver a complete convergence analysis, including stability and regularization properties. Further, we show that our new method is competitive by testing it with real data in the complete electrode model of 2D electrical impedance tomography.
Calculations of shake-up satellites intensities in photoelectron spectra by generalized configuration interaction method
Authors: Yarzhemsky V G , Chernysheva L V
Published: July 2022

Satellites i.e. two-hole-one-particle states appear due to many-electron correlations in photoelectron spectra in addition to main lines corresponding to one-hole states. The correct assignment of these states is important for understanding the photoionization processes and for materials analysis by photoelectron spectroscopy. In the present work two different existing methods, which use overlap or Coulomb interaction matrix elements are considered and a new method is proposed. In this technique many-electron effects of satellites origin and interactions between satellite states are accounted for simultaneously by solving secular matrix. The method is applied to satellite states 2p
−23p(4p), 2p
−23s, 2p
−23d of Ne photoionization for which contradiction between two interpretations existed. The results of calculations unambiguously support one the interpretations.
Annealing temperature dependence of band alignment of NiO/β-Ga2O3
Authors: Xia Xinyi , Li Jian-Sian , Chiang Chao-Ching , Yoo Timothy Jinsoo , Ren Fan , Kim Honggyu , Pearton S J
Published: July 2022

The band alignment of sputtered NiO on β-Ga2O3 was measured by x-ray photoelectron spectroscopy for post-deposition annealing temperatures up to 600 °C. The band alignment is type II, staggered gap in all cases, with the magnitude of the conduction and valence band offsets increasing monotonically with annealing temperature. For the as-deposited heterojunction, ΔE
V = −0.9 eV and ΔE
C = 0.2 eV, while after 600 °C annealing the corresponding values are ΔE
V = −3.0 eV and ΔE
C = 2.12 eV. The bandgap of the NiO was reduced from 3.90 eV as-deposited to 3.72 eV after 600 °C annealing, which accounts for most of the absolute change in ΔE
V−ΔE
C. Differences in thermal budget may be at least partially responsible for the large spread in band offsets reported in the literature for this heterojunction. Other reasons could include interfacial disorder and contamination. Differential charging, which could shift peaks by different amounts and could potentially be a large source of error, was not observed in our samples.
First-principles calculation of gate-tunable ferromagnetism in magic-angle twisted bilayer graphene under pressure
Authors: Chen Xiao , Liu Shuanglong , Fry James N , Cheng Hai-Ping
Published: July 2022

Magic-angle twisted bilayer graphene (MATBG) is notable as a highly tunable platform for investigating strongly correlated phenomena such as unconventional superconductivity and quantum spin liquids, due to easy control of doping level through gating and sensitive dependence of the magic angle on hydrostatic pressure. Experimental observations of correlated insulating states, unconventional superconductivity and ferromagnetism in MATBG indicate that this system exhibits rich exotic phases. In this work, using density functional theory calculations in conjunction with the effective screening medium method, we find the MATBG under pressure at a twisting angle of 2.88∘ and simulate how its electronic states evolve when doping level and electric field perpendicular to plane are tuned by gating. Our calculations show that, at doping levels between two electrons and four holes per moiré unit cell, a ferromagnetic (FM) solution with spin density localized at AA stacking sites is lower in energy than the nonmagnetic solution. The magnetic moment of this FM state decreases with both electron and hole doping and vanishes at four electrons/holes doped per moiré unit cell. Hybridization between the flat bands at the Fermi level and the surrounding dispersive bands can take place at finite doping. On increasing the out-of-plane electric field at zero doping, a transition from the FM state to the nonmagnetic one is seen. An investigation of impurity effects shows that both absorption of

O

2

molecules and occurrence of Stone–Wales impurities suppress the FM state, and the mechanisms are understood from our calculations. We also analyze the interlayer bonding character due to flat bands via Wannier functions. Finally, we report trivial band topology of the flat bands in the FM state at a certain doping level.
First-principle study of the effect of point defects on the activity, carrier lifetime, and photocatalytic performance of ZnO:(S/Se/Te) system
Authors: Gu Yulan , Hou Qingyu , Zhao Chunwang
Published: July 2022

The effect of S/Se/Te-doped ZnO system on photocatalytic performance has been extensively studied. However, theoretical computational studies on S/Se/Te-doped ZnO systems containing O or Zn vacancies are lacking. Previous theoretical computational studies have also ignored the problem of unintentional introduction of H-interstitial impurities in the semiconductor fabrication process in a vacuum environment. In this paper, first-principle study is used to investigate S/Se/Te-doping and the vacancy (VO or VZn) and H gap coexistence on the photocatalytic properties of ZnO. The results showed that the Zn35SHiO35 system has the best hole life, strong activity, obvious red shift of absorption spectrum, and strong oxidation reaction. This has good theoretical reference value to be used as a photocatalyst for oxidative reaction to decompose water to produce H2.
Lower bounds for the number of limit cycles in a generalised Rayleigh–Liénard oscillator
Authors: Euzébio Rodrigo D , Llibre Jaume , Tonon Durval J
Published: July 2022

In this paper a generalised Rayleigh–Liénard oscillator is consider and lower bounds for the number of limit cycles bifurcating from weak focus equilibria and saddle connections are provided. By assuming some open conditions on the parameters of the considered system the existence of up to twelve limit cycles is provided. More precisely, the approach consists in perform suitable changes in the sign of some specific parameters and apply Poincaré–Bendixson theorem for assure the existence of limit cycles. In particular, the algorithm for obtaining the limit cycles through the referred approach is explicitly exhibited. The main techniques applied in this study are the Lyapunov constants and the Melnikov method. The obtained results contemplate the simultaneity of limit cycles of small amplitude and medium amplitude, the former emerging from a weak focus equilibrium and the latter from homoclinic or heteroclinic saddle connections.
Evolution of surface states of antiferromagnetic topological insulator MnBi2Te4 with tuning the surface magnetization
Authors: Yang Zhilong , Zhang Haijun
Published: July 2022

The interplay between magnetism and topologically non-trivial electronic states is an important subject in condensed matter physics. Recently, the stoichiometric intrinsic magnetic material MnBi2Te4 provides an ideal platform to study the magnetic topological phenomena, such as quantum anomalous Hall effect, axion insulator state, topological magnetoelectric effect. However, it is still controversial whether the topological surface state in the (111) plane is gapped or not. Here, we develop an effective method to study different surface magnetizations based on first-principles calculations. Then we investigate the band dispersions, the Fermi surfaces (FSs), the quasiparticle interferences (QPIs) and the spin texture of topological surface states of MnBi2Te4 with tuning the surface magnetization. We find that the surface magnetization has significant effects on the surface states. Our results also indicate that the symmetry breaking of FSs and QPIs may be a useful way to determine the possible surface magnetization of MnBi2Te4.
Gravity-induced geometric spin Hall effect of freely falling quantum particle
Authors: Wang Zhen-Lai , Chen Xiang-Song
Published: July 2022

We discuss a new gravitational effect that the wave packet of a free-fall quantum particle undergoes a spin-dependent transverse shift in Earth’s gravitational field. This effect is similar to the geometric spin Hall effect (GSHE) (Aiello 2009 et al
Phys. Rev. Lett.
103 100401 ), and can be called gravity-induced GSHE. This effect suggests that the free-fall wave packets of opposite spin-polarized quantum particles can be split in the direction perpendicular to spin and gravity.
Research on the On-orbit Background of the Hard X-Ray Imager Onboard ASO-S
Authors: Liu Wei , Chen Deng-Yi , Jiang Xian-Kai , Wu Jian , Zhang Zhe , Hu Yi-Ming , Su Yang , Chen Wei , Ma Tao
Published: July 2022

The space environment background of various particle fluxes of the Hard X-ray Imager (HXI), one of the payloads of the Advanced Space-based Solar Observatory (ASO-S) spacecraft, is investigated and presented. Different approaches are used to obtain the input information on various space environment particles (protons, alpha particles, electrons, positrons, neutrons, and photons). Some special regions (SAA and radiation belt) are also taken into account. The findings indicate that electrons are the primary background source in the radiation belt. Due to the large background flux generated by electrons, HXI cannot effectively observe solar flares in the radiation belt. Outside the radiation belt, primary protons and albedo photons are the main sources of background at low and high magnetic latitudes respectively. The statistical analysis of the flare and background spectra shows that the errors of the flare energy spectrum observation are mainly concentrated in the high energy band, and the detector still has a certain spectrum observation capability for flares of C-class and below in the low energy band of the non-radiation belt. The imaging observation of flares of C-class and below is significantly affected by the accuracy of background subtraction. The energy band with the best signal-to-noise ratio is from 10 to 50 keV, which can be used to monitor the formation and class of flares.