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It is imperative to have an in-depth understanding of the mechanism of action for the role of moisture in a coal matrix during coal spontaneous combustion, not only for preventing fires in the coal industry but also for reducing emissions of hazardous gases. In this study, the method of isotope tracing was first introduced to study the mechanism of moisture in the spontaneous combustion of coal. Moisture in a coal matrix was labeled separately using D2O and H218O, and the coal samples with internal moisture and external moisture were prepared by controlling the drying temperature. Coal samples with different isotopic moisture were heated using a spontaneous combustion apparatus. The gaseous products (CO2, CO, and CH4) were measured using a GC-950 gas chromatography equipped with a flame photometric detector, and simultaneously, the isotopic gases (including C18O, C18O2, CH3D) were timely monitored using an online mass spectrometer. The appearance of isotopic gases directly proved that the moisture could participate in the spontaneous combustion of coal in atomic level, and the moisture in the coal matrix is involved in the spontaneous combustion of coal through chemical reaction. Based on the experimental results, the pathways of the oxygen atom and H atom from the moisture participating in the production of isotopic gases were investigated. The reaction mechanism of moisture participating in the spontaneous combustion of coal was also explored based on the migration law of oxygen and hydrogen atoms of H2O molecule in coal matrix. [ABSTRACT FROM AUTHOR]

A profound comprehension of friction and wear mechanisms is essential for the design and development of high-performance polymeric materials for tribological application. However, it is difficult to deeply investigate the polymer friction process in situ at the micro/mesoscopic scale by traditional research methods. In recent years, molecular dynamics (MD) simulation, as an emerging research method, has attracted more and more attention in the field of polymer tribology due to its ability to show the physicochemical evolution between the contact interfaces at the atomic scale. Herein, we review the applications of MD in recent studies of polymer tribology and their research focuses (e.g., tribological properties, distribution and conformation of polymer chains, interfacial interaction, frictional heat, and tribochemical reactions) across three perspectives: all-atom MD, reactive MD, and coarse-grained MD. Additionally, we summarize the current challenges encountered by MD simulation in polymer tribology research and present recommendations accordingly, aiming to provide several insights for researchers in related fields. [ABSTRACT FROM AUTHOR]

The oxide supports play a crucial role in anchoring and promoting the active metal species by geometric confinement and chemical interaction. The design and synthesis of the well-defined oxide support with specific morphology such as size, shape, and exposed facets have attracted extensive research efforts, which directly reflects on their catalytic performance. In this study, using an Au/CeO2-nanorod model catalyst, we demonstrate an edge effect on the Au/CeO2 interfacial structure, which shows a prominent effect on the structure–performance relationship in the CO oxidation reaction. This specific "edge-interface" structure features an "edge-on" Au nanoparticles position on rod-shaped CeO2 support, confirmed by atomic-scale electron microscopy characterization, which introduces additional degrees of freedom in coordination environment, chemical state, bond length, and strength. Combined with theocratical calculations and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) investigations, we confirmed that this "edge-interface" has distinct adsorption properties due to the change of O vacancy formation energy as well as the chemical states of Au resulting from the electron transfer and redistribution between the metal and the support. These results demonstrate a non-conventional geometric effect of rod-shaped supported metal catalysts on the catalytic performance, which could provide insights into the atomic-precise utilization of catalysts. [ABSTRACT FROM AUTHOR]

A profound comprehension of friction and wear mechanisms is essential for the design and development of high-performance polymeric materials for tribological application. However, it is difficult to deeply investigate the polymer friction process in situ at the micro/mesoscopic scale by traditional research methods. In recent years, molecular dynamics (MD) simulation, as an emerging research method, has attracted more and more attention in the field of polymer tribology due to its ability to show the physicochemical evolution between the contact interfaces at the atomic scale. Herein, we review the applications of MD in recent studies of polymer tribology and their research focuses (e.g., tribological properties, distribution and conformation of polymer chains, interfacial interaction, frictional heat, and tribochemical reactions) across three perspectives: all-atom MD, reactive MD, and coarse-grained MD. Additionally, we summarize the current challenges encountered by MD simulation in polymer tribology research and present recommendations accordingly, aiming to provide several insights for researchers in related fields.

Atom Probe Tomography (APT) is a test analysis technique that provides quantitative three-dimensional element and isotope analysis at subnanometer resolution, with extremely high spatial resolution and low detection limits. Compared with traditional geological analysis techniques, APT has unique technical advantages, which can be used to analyze the elemental composition of minerals <0.0007μm³ in volume, reveal the complexity of mineral composition at the nanoscale, and provide a new understanding of the geological evolution process. APT has been in development for over 50 years, and continuous technological advancements have led to its wider application range. At the beginning of APT design, it was only used for conductive materials. From the end of the 20th century to the beginning of the 21st century, the application of laser pulse mode enabled APT to be applied to semiconductors and insulating materials, and the application of Local Electrode TM Atom Probe (LEAP) improved several key parameters such as the data acquisition rate and mass resolution of APT by several orders of magnitude. At present, most of the geological application work of APT is carried out by LEAP in laser-assisted mode. In recent years, the unique technical advantages of APT have attracted increasing attention in geological research, and their advantages in ore deposit research have become more prominent. Some important research results have been published. However, on the whole, its application in ore deposits and even geology is still in its infancy. The development history, basic principle, selection method of area of interest and needle tip sample preparation of APT are briefly introduced in this paper. Based on this, representative application achievements of APT in ore deposit research by domestic and foreign scholars in recent years are collected and summarized. In ore deposit research, APT is mainly applied in three aspects: the occurrence states of ore-forming elements, nanoscale inclusions, and stable isotope composition. At present, most research results focus on the analysis of the occurrence status of ore-forming elements, especially pyrite or other minerals with simple chemical composition related to gold deposits. APT has successfully revealed three main occurrence states of ore-forming elements on the atomic scale: uniform distribution, nanoparticle and enrichment at low angle grain boundaries and dislocations. For example, gold can be uniformly distributed in the form of dispersed lattice bound gold in the arsenic-rich overgrowth rim of pyrite, and can form nanoclusters of different sizes in arsenopyrite. It can also host in the low angle boundary of pyrite related to deformation . In terms of nano inclusions and stable isotope composition, the research mainly focuses on pyrite nano fluid inclusions and S isotopes. For example, nano telluride inclusions along pyrite fractures in low-sulfidation type epithermal Au-Ag-Te deposit and the method for obtaining quantitative δ 34S measurement value from APT datasets of pyrite. The relevant results are shown in Fig.E.1. So far, the applications of APT in ore deposits research have mainly focused on the occurrence state of oreforming elements, achieving three-dimensional visualization of atomic scale element distribution that was previously unimaginable, providing a new perspective for people to understand and explain the ore-forming process. In terms of nano inclusions and stable isotope composition, although the applications of APT are not as rich as the former, some important new understandings have been obtained, showing a good application prospect. While APT is rapidly developing in the field of ore deposits, there are still many problems to be solved in its practical application. For example, the extremely small sample volume, time-consuming selection of specific areas, the background noise carried by the mass spectrometry itself, the correct interpretation of complex spectral peaks, and the accuracy of data three-dimensional reconstruction. However, it is foreseeable that with the continuous progress of technology, APT will become more popular and easier to use, increasing numbers of deposit researchers will pay attention to APT, and more ore deposit samples with complex types, structures and chemical compositions will apply this technology for in-depth research, which may change or even completely subvert our understanding of some basic scientific problems in ore deposits. [ABSTRACT FROM AUTHOR]

Calcium-aluminum-rich inclusions (CAIs) in chondritic meteorites are composed of refractory minerals thought to be the first solids to have formed in the solar nebula. Among them, hibonite, nominally CaAl12O19, holds particular interest because it can incorporate significant amounts of Ti into its crystal structure in both Ti3+ and Ti4+ oxidation states. The relative amounts of these cations that are incorporated reflect the redox conditions under which the grain formed or last equilibrated and their measurement can provide insight into the thermodynamic landscape of the early solar nebula. Here we develop a new method for the quantification of Ti oxidation states using electron energy-loss spectroscopy (EELS) in an aberration-corrected scanning transmission electron microscope (STEM) to apply it to hibonite. Using a series of Ti-bearing oxides, we find that the onset intensity of the Ti L2,3 edge decreases with increasing Ti-oxidation state, which is corroborated by simulated Ti-oxide spectra using first-principles density-functional theory. We test the relationship on a set of synthetic hibonite grains with known Ti4+/ΣTi values and apply the developed method on a hibonite grain from a compact type A inclusion in the Northwest Africa (NWA) 5028 CR2 carbonaceous chondrite. The STEM-EELS data show that the chondritic hibonite grain is zoned with a Ti4+/ΣTi ratio ranging from 0.78 ± 0.04 to 0.93 ± 0.04 over a scale of 100 nm between the core and edge of the grain, respectively. The Ti substitution sites are characterized by experimental and calculated high-angle annular-dark-field (HAADF) images and atomic-level EEL spectrum imaging. Simulated HAADF images reveal that Ti is distributed between the M2 and M4 sites while Mg sits on the M3 site. Quantitative energy-dispersive X-ray spectroscopy shows that this grain is also zoned in Al and Ti. The Mg distribution is not well correlated with that of Ti and Ti4+/ΣTi at the nanoscale. The spatial decoupling of the element composition and Ti-oxidation states suggests a multistage evolution for this hibonite grain. We hypothesize that Ti and Mg were incorporated into the structure during condensation at high temperature through multiple reactions. Transient heating, presumably in the solar nebula, adds complexity to the crystal chemistry and potentially redistributed Ti and Mg. Concurrently, the formation of oxygen vacancies as a result of a reducing gas, led to the reduction of Ti4+ to Ti3+. The multiple defect reactions occurring in this single hibonite crystal preclude a simple relationship between the Ti4+/ΣTi and the fO2 of formation. However, moving forward, these measurements are fundamental inputs for modeling of the thermodynamic conditions under which hibonite formed in the early solar nebula. [ABSTRACT FROM AUTHOR]

• Atomic-scale material removal mechanism for double nanoscratches of GaN. • Molecular dynamics simulation reveals material deformation and subsurface damage mechanism. • The significant increase in lateral force of the second nanoscratch is the cause of brittle fracture. • High-density stacking fault bands suppress the extension of subsurface damage. • Experimental validation for material behaviors and subsurface damage. Gallium nitride (GaN) is an important third-generation semiconductor material. However, due to its high hardness, high brittleness and anisotropy, the material removal efficiency of GaN during ultraprecision machining is low, and subsurface damage easily occurs. In order to achieve high-efficiency and low-damage ultra-precision machining, the model of double nanoscratches is innovatively utilized to investigate the mechanical behavioral of GaN at the atomic scale. Specifically, double nanoscratches experiments and corresponding molecular dynamics (MD) simulations were carried out on GaN (0001) crystal plane along the [ 10 1 ¯ 0 ] and [ 1 2 ¯ 10 ] crystal directions to reveal the material removal, deformation and subsurface damage mechanisms of GaN under anisotropic conditions. The results show that the plastic removal of GaN can be realized by setting loading force and scratch spacing. Scratching along the [ 1 2 ¯ 10 ] crystal direction has a greater ductile-brittle transition load force than the [ 10 1 ¯ 0 ] crystal direction. MD analysis shows that the downward-extending prismatic slip produced by scratching along the [ 10 1 ¯ 0 ] crystal direction is the cause of crack extension to the subsurface during the experiment. As the load force increases, the surface cracks of the double scratches expand and intersect, inducing streak-like brittle fracture. The significant increase in the lateral force of the second scratch is the main reason for the brittle fracture in the double scratch experiment. After the double nanoscratches experiment, the damage presented on the GaN subsurface mainly includes atomic scale damage such as amorphization, stacked laminations, polycrystalline nanoscratch, and phase transition. The Stacking fault bands around the damage zone inhibit the damage extension. The second scratch generates a large number of dislocations in the overlap zone and attenuates the subsurface amorphization under the influence of dislocation strengthening effect. [Display omitted] [ABSTRACT FROM AUTHOR]

Electron back scatter diffraction instrument and high-resolution transmission electron microscope were used to observe and characterize the twin-twin interaction behavior in tensile-deformed 120Mn13 steel at the atomic scale. Here the whole twin-twin interaction behavior was divided into three processes and the deformation mechanisms of each process were revealed, including the interaction between the incident twin and the coherent twin boundary of the barrier twin, which can lead to a twinning or detwinning process of the barrier twin, the trigger formation of secondary twins and the formation of second order twins in the intersection region. Based on the Thomson tetrahedron, the dislocation movements in different twin-twin interaction processes were systematically described, and the possibility of dislocation reactions were discussed in energy. The interaction mechanism of the microscopic zero-stain twin (MZST) was proposed for the first time, and its differences from the classical twin-twin interaction mechanism were expounded. Present work further enriches the twin-twin interaction behavior in face centered cubic metallic materials. It can also guide the in-depth understanding of the classical twin-twin interaction behaviors and be used to explain the formation of classical secondary and second order twins. [Display omitted] • Three or four types of twin variants can be generated directly from the matrix of one austenite grain. • The interaction between the incident twin and the CTB can lead to a twinning or detwinning process of the barrier twin. • Two stress-triggered formation mechanisms of the secondary twin during twin-twin interaction were proposed. • Two types of intersecting twins were observed in deformed 120Mn13 steel and two possible formation mechanisms of the second order twin were proposed. [ABSTRACT FROM AUTHOR]

Honeycomb-layered phases like Na 3 Ni 2 SbO 6 have been extensively researched as high-voltage and high-rate capability cathode materials for sodium-ion batteries. However, our understanding of the structural stability and dynamic reaction mechanisms of Na 3 Ni 2 SbO 6 cathode during cycling, especially at atomic-scale, remains limited. Here, we track the microstructure evolution during extraction of Na+ ions in Na 3 Ni 2 SbO 6 cathode at atomic scale in an aberration-corrected transmission electron microscope. The electron beam irradiation that can provide a driving force for the Na+ ion migration, allows us to mimic the battery charge process. By controlling the electron beam dose, we study the structure evolution behavior to obtain insights into understanding the work principle and failure mechanism of Na 3 Ni 2 SbO 6 cathode under different charge rate conditions. We find that the real-time structural evolution and ion migration pathways of Na 3 Ni 2 SbO 6 cathode are distinct under different electron beam doses. High-dose irradiation reveals Na ion depletion, surface cracks, and phase transformations, mimicking rapid capacity decay. In contrast, low-dose irradiation shows slower ion migration, ordered Na vacancy formation, and maintaining structural integrity, which more closely resembles the electrochemical process of actual battery. This study provides an atomistic understanding of the structural stability and Na ions deintercalation mechanism in Na 3 Ni 2 SbO 6 cathodes, offering new insights into optimizing electrode materials. [Display omitted] • Real-time visualization of atomic-scale structural dynamics and Na+ ion migration pathways within Na 3 Ni 2 SbO 6 cathodes. • Low-dose electron beam irradiation can simulate Na+ ion migration, mimicking the charging process of a sodium-ion battery. • High-dose electron beam reveals degradation mechanisms, including capacity fade, structure damage, and phase transitions. [ABSTRACT FROM AUTHOR]

Alloy nanostructures have been extensively exploited in both thermal and electrochemical catalysis due to their beneficial "synergetic effects" and being cost-effective. Understandings of the alloy nanostructures including phases, interfaces, and chemical composition are prerequisites for utilizing them as efficient electrocatalysts. Here, we use carbon-supported CuAu nanoparticles as a model catalyst to demonstrate the phase-separation induced variation of electrochemical performance for the CO2 reduction reaction. Driven by thermal oxidation, the CuOx phase gradually separates from the original CuAu nanoparticles, and different carbon supports, i.e., graphene vs. carbon nanotube lead to a reversed trend in the selectivity towards CO production. Through detailed structural and chemical analysis, we find the extent of phase separation holds the key to this variation and could be used as an effective method to tune the electrochemical properties of the alloy phase. [ABSTRACT FROM AUTHOR]

Metal—zeolite catalysts are vital in chemical and fuel production for their great stability, stereo-selectivity, and atom economy. When metal species keep shrinking their sizes to the subnanometer region, their spatial distribution in the zeolite framework/channels could have a great impact on their catalytic performance. Here, we precisely control the Pt species loaded on a silicalite-1 zeolite and characterize their structural status to the catalytic performance for CO oxidation. We find that Pt species exits as few-atom clusters encapsulated in the channels and destructively embedded Pt nanoparticles in the framework, besides the conventional surface-supported Pt. By utilizing effective Pt sites and limiting their sizes in the zeolite, we can maximize the catalytic CO oxidation performance of 1 at.% Pt-loaded zeolite catalysts to achieve a T100 as low as 90 °C and a stable reaction above 216 h. [ABSTRACT FROM AUTHOR]

The atomic layer technique is generating a lot of excitement and study due to its profound physics and enormous potential in device fabrication. This article reviews current developments in atomic layer technology for spintronics, including atomic layer deposition (ALD) and atomic layer etching (ALE). To begin, we introduce the main atomic layer deposition techniques. Then, in a brief review, we discuss ALE technology for insulators, semiconductors, metals, and newly created two-dimensional van der Waals materials. Additionally, we compare the critical factors learned from ALD to constructing ALE technology. Finally, we discuss the future prospects and challenges of atomic layer technology in the field of spinronics. [ABSTRACT FROM AUTHOR]

The potential of high entropy oxides (HEOs) as high-performance energy storage materials and catalysts has been mainly understood through their bulk structures. However, the importance of their surfaces, which may play an even more critical role, remains largely unknown. In this study, we employed advanced scanning transmission electron microscopy to investigate the atomic-scale structural and chemical responses of CeYLaHfTiZrO x HEOs to high-temperature redox environments. Our observations reveal dynamic elemental and structural reconstructions in the surface of HEOs under different gas environments, contrasting with the high stability of the bulk structure. Notably, the surfaces of HEO particles consistently exhibit abundant oxygen vacancies, regardless of the redox environment. These findings indicate that HEOs offer distinct advantages in facilitating chemical and electrochemical reactions, relying on oxygen vacancies. Our results also suggest that the exceptional performance of HEOs in energy storage applications arises from surface structural and chemical adaptability.

Understanding the deformation mechanisms of rutile titanium dioxide (TiO2) nanowires (NWs) helps to improve the working reliability of TiO2-based nanoelectrical–mechanical systems and better apply strain engineering to these materials. This work investigated the bending deformation mechanisms at the atomic scale using in situ transmission electron microscopy (TEM) near room temperature. Large bending strains of 3.0% to 5.1% could be observed on individual TiO2 NWs near room temperature. The large bending deformation was attributed to the formation of rich stacking faults (SFs) lying on (101̅) planes and the nucleation and glide of extended dislocations belonging to the {101̅}⟨101⟩ slip system. [ABSTRACT FROM AUTHOR]

The evolution of hydrogen from water using renewable electrical energy is a topic of current interest. Pt/C exhibits the highest catalytic activity for the H2 evolution reaction (HER), but scarce supplies and high cost limit its large‐scale application. Atomic active centers in single‐atom catalysts, single‐atom alloys, and catalysts with two atom sorts exhibit maximum atomic efficiency, unique structure, and exceptional activity for the HER. Interactions between well‐defined active sites and supports are known to affect electron transfer and dramatically accelerate the reaction. This Review first highlights methods for studying atomic active centers for the HER. Then, active sites with different coordination configurations are described. Active centers with one metal atom, two different metal atoms as well as nonmetal atoms are analyzed at the atomic scale. Finally, future research perspectives are proposed. [ABSTRACT FROM AUTHOR]

A novel molecular model of vulcanized styrene-butadiene rubber (SBR) was developed and experimentally verified to elucidate the enhanced tribological performance of vulcanized SBR over raw SBR. Vulcanization was modeled by cross- or self-linkages of sulfur (S) atoms with carbon (C) atoms in molecular chains. Frictional models were developed for vulcanized and raw styrene-butadiene rubber-ferrum (SBR-Fe) to study the atomic behavior at the frictional interface. The results at the atomic scale show considerable reductions in the coefficient of friction (COF) and the interfacial temperature of approximately 45.8% and 13.27% for the vulcanized SBR matrix, respectively, from those of raw SBR. In addition, the relative concentration (RC), the radial distribution function (RDF) and interaction energy of the vulcanized SBR are 21.61%, 6.68% and 60.12% lower than those of the raw SBR, respectively. The resulting decrease in the real contact area, adhesion and contact temperature at the interface can significantly improve the tribological properties of the vulcanized SBR over those of raw SBR. The results of this research study show how vulcanization can enhance the tribological properties of polymer composites at the atomic scale. [ABSTRACT FROM AUTHOR]

• Deformation twins with zero net macroscopic strain were frequently distributed in coarse-grained 120Mn13 steel under different engineering stresses, which revealed the fact that the zero-strain twin is ubiquitous in coarse-grained fcc metallic materials. • A new 9R phase with different stacking sequences was first discovered and defined as 9R-Ⅱ to distinguish it from the classical 9R phase. • Three types of precursors were discussed for the zero-strain twin formation. • A new formation and growth mechanism of zero-strain twins based on the 9R phase transformation was proposed. High-resolution transmission electron microscope was used to observe and characterize the different formation stages of zero-strain twins in uniaxial tensile-deformed 120Mn13 steel at the atomic scale, which revealed the growth process of zero-strain twins in coarse-grained austenitic manganese steels. Here, plenty of zero-strain twins are observed in deformed 120Mn13 steel and they can be formed by three types of precursors. Their processes of expansion and connection, thickening and thinning can be carried out through the transformation of 9R phase with the matrix and the twin. A new 9R phase with different stacking sequences is firstly discovered and defined as 9R-Ⅱ to distinguish it from the classical 9R phase (9R-Ⅰ). 9R-Ⅰ and 9R-Ⅱ have the same lattice structure but different internal atomic arrangements and satisfy a twin-like relationship. In addition, a new formation mechanism of zero-strain twins based on the 9R phase transformation is proposed. [ABSTRACT FROM AUTHOR]

Re doping is an essential way to improve the high temperature mechanical properties of nickel-based single crystal superalloy (NBSCS). However, how the doped Re affects the mechanical properties of NBSCS is still unclear, and a quantitative description is lacking. This paper attempts to study the influence of Re doping on plastic deformation mechanisms of NBSCS at atomic scale. First, the grand-canonical Monte Carlo method was employed to determine the distribution of Re atoms within the two-phase microstructure of NBSCS. Then, the molecular dynamics simulations were carried out to study the effect of Re doping on the dislocation motion and evolution during plastic deformation, with a focus on two important deformation mechanisms in NBSCS, i.e., dislocation gliding in the hairpin-like shape in the narrow γ matrix channel and dislocation cutting into the γ′ precipitation from the γ matrix. The results show that Re atoms prefer to segregate at the γ/γ′ interface. The increase of Re concentration in NBSCS can significantly improve both the critical stress of dislocations gliding in the γ matrix channel and the critical stress of dislocation cutting into the γ′ precipitation. These simulation results are qualitatively consistent with experimental observations. Based on these atomic scale simulations, two quantitative models for screw dislocation gliding in a hairpin-like shape in the γ matrix channel and dislocation cutting into the γ′ precipitation in the super-dislocation pair that take into account the Re doping effects have been proposed. The good agreement between the molecular dynamics simulation and the model prediction suggests that these quantitative models can be used for up-scale simulations of the dislocation movement and evolution in the presence of Re doping in NBSCS. • Re segregation near the γ/γ′ interface was obtained by GCMC calculation. • The critical stresses for leading dislocation cutting into the γ′ precipitation and dislocation gliding in a hairpin-like shape in γ matrix both increase with the increasing Re concentration. • Two theoretical models were proposed to describe the critical stresses of the dislocation mechanisms. [ABSTRACT FROM AUTHOR]

The generally nonpolar SrTiO 3 has attracted more attention recently because of its possibly induced novel polar states and related paraelectric-ferroelectric phase transitions. By using controlled pulsed laser deposition, high-quality, ultrathin, and strained SrTiO 3 layers were obtained. Here, transmission electron microscopy and theoretical simulations have unveiled highly polar states in SrTiO 3 films even down to one unit cell at room temperature, which were stabilized in the PbTiO 3 /SrTiO 3 /PbTiO 3 sandwich structures by in-plane tensile strain and interfacial coupling, as evidenced by large tetragonality (∼1.05), notable polar ion displacement (0.019 nm), and thus ultrahigh spontaneous polarization (up to ∼50 μC/cm 2 ). These values are nearly comparable to those of the strong ferroelectrics as the PbZr x Ti 1- x O 3 family. Our findings provide an effective and practical approach for integrating large strain states into oxide films and inducing polarization in nonpolar materials, which may broaden the functionality of nonpolar oxides and pave the way for the discovery of new electronic materials.

Integrating nanoscale optoelectronic functions is vital for applications such as optical emitters, detectors, and quantum information. Lanthanide atoms show great potential in this endeavor due to their intrinsic transitions. Here, we investigate Er adatoms on Si(100)-2×1 at 9 K using a scanning tunneling microscope (STM) coupled to a tunable laser. Er adatoms display two main adsorption configurations that are optically excited between 800 and 1200 nm while the STM reads the resulting photocurrents. Our spectroscopic method reveals that various photocurrent signals stem from the bare silicon surface or Er adatoms. Additional photocurrent peaks appear as the signature of the Er adatom relaxation, triggering efficient dissociation of nearby trapped excitons. Calculations using density functional theory with spin-orbit coupling correction highlight the origin of the observed photocurrent peaks as specific 4f→4f or 4f→5d transitions. This spectroscopic technique can facilitate optoelectronic analysis of atomic and molecular assemblies by offering insight into their intrinsic quantum properties.

Structural modulation of catalytic nanostructures and fundamental understanding of their active sites at the atomic scale are important for predicting and improving the catalytic properties of nanostructures. Here, we prepared quasi-one-dimensional (1D) metal molybdenum (Mo) chains confined in atom-thick molybdenum disulfide (MoS 2), referred henceforth as Mo/MoS 2 nanosheets, and evaluated their hydrogen evolution reaction (HER) properties. The experiment and theoretical calculations show that the quasi-1D Mo chain with unsaturated coordination exhibits high HER activity. The unsaturated Mo sites in the chains increase the carrier density and facilitate the diffusion of hydrogen along the chains, mimicking an atomic scale reactor which leads to an experimentally observed enhanced catalytic performance. Within the framework of Volmer-Tafel model, the calculated kinetic barrier for H 2 evolution is only 0.48 eV for Mo/MoS 2 , which is significantly lower than that for the Pt (111) surface (∼0.8 eV). In particular, Mo/MoS 2 nanosheets supported on reduced graphene oxide (Mo/MoS 2 /RGO) outperformed commercial Pt on glassy carbon (Pt/C) in the practically meaningful high-current region (>140 mA cm−2) in 0.5 M H 2 SO 4 solution and (15 mA cm−2) in 1.0 M NaOH solution, demonstrating that the Mo/MoS 2 /RGO could potentially replace Pt catalysts in practical HER systems. Additionally, this study provides crucial insights into the role of active centers in catalysis through a model-structure-performance relationship, thus pointing the way to a commercially viable technology for HER. Image 1 • High activity for HER catalytic behavior. • Novel 1D Mo atomic chain structure. • Low kinetic barrier for H 2 evolution. [ABSTRACT FROM AUTHOR]

Core–shell noble metal catalysts have gained significant attention in the past few decades, as they not only reduce the use of noble metals effectively but also exhibit unique properties derived from the synergistic effect between core and shell metals. In particular, regulating the surface structure of shells to maximize the atomic utilization efficiency of noble metals is critically important. Controlling the shell thickness of noble metal catalysts at the atomic level as an efficient approach to realize this goal has been attracting growing attention; this approach involves the formation of ultrathin shells (typically 2–6 atomic layers), monolayers, or even atomically dispersed noble metals embedded in the host metal. These strategies drive the core/support metals to improve the number of active sites and the intrinsic activity of the deposited noble metals remarkably, meanwhile minimizing the usage of noble metals. Herein, recent advances regarding atomic control of the core–shell noble metal catalysts is reviewed, with focus on the surface regulation. First, synthesis methods and surface structures are summarized, and then catalytic applications of these architectures are highlighted. Atomic control: Recent advances regarding atomic control of the core–shell noble metal catalysts are reviewed, with a focus on control of the shell thickness at the atomic level. These strategies drive the core/support metals to improve the number of active sites and the intrinsic activity of deposited noble metals remarkably, whilst minimizing the use of noble metals (see figure). [ABSTRACT FROM AUTHOR]

The observation of fracture behaviors in perfect and twinned B 4 C crystals via in situ transmission electron microscopy (TEM) mechanical testing is reported. The crystal structure of the synthesized B 4 C, composed of B 11 C icosahedra connected by boron-deficient C-▫-C chains in a chemical formula of B 11 C 3 , is determined by state-of-the-art aberration-corrected scanning TEM. The in situ TEM observations reveal that cracking is preferentially initiated at the twin boundaries (TBs) in B 4 C under both indentation and tension loading. The cracks then propagate along the TBs, thus resulting in the fracture of B 4 C. These results are consistent with the theoretical calculations that show that TBs have a softening effect on B 4 C with amorphous bands preferentially nucleated at the TBs. These findings elucidate the atomic arrangement and the role of planar defects in the failure of B 4 C. Furthermore, they can guide the design of advanced superhard materials via planar defect control., (© 2022 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

Abstract Twin boundary can both strengthen and soften nanocrystalline metals and has been an important path for improving the strength and ductility of nano materials. Here, using in-lab developed double-tilt tensile stage in the transmission electron microscope, the atomic scale twin boundary shearing process was in situ observed in a twin-structured nanocrystalline Pt. It was revealed that the twin boundary shear was resulted from partial dislocation emissions on the intersected {111} planes, which accommodate as large as 47% shear strain. It is uncovered that the partial dislocations nucleated and glided on the two intersecting {111} slip planes lead to a transition of the original <110> symmetric tilt ∑3/(111) coherent twin boundary into a <110> symmetric tilt ∑9/(114) high angle grain boundary. These results provide insight of twin boundary strengthening mechanisms for accommodating plasticity strains in nanocrystalline metals. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract: Understanding the reaction processes of electrode and electrolyte materials is important for achieving high‐performance lithium‐ion batteries (LIBs). Currently, transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) can readily characterize the structural and chemical features of these materials from the micrometer scale to the atomic scale. In situ (S)TEM can further monitor their non‐ or quasi‐equilibrated states in real time. Here, the recent progress in unraveling the crystal and electronic structures of the electrode and solid‐electrolyte materials using ex situ and in situ (S)TEM is reviewed. Three fundamental functions, including imaging, diffraction, and spectroscopy, are jointly used to decipher the configuration of the defects and ordering, the variations near the surfaces and across the interfaces, and the evolution of the coexisting phases. Novel and deep insights are proposed for the material growth, reaction, and capacity fading mechanisms. Advanced (S)TEM studies for LIB materials pose numerous challenges and perspectives, including the development and application of local diffraction analysis, large‐scale phase mapping techniques, 3D reconstruction, and cryoelectron microscopy, which are further discussed. [ABSTRACT FROM AUTHOR]

The effects of length and content of chain branching on the mechanical properties of polyethylene (PE) in atomic scale were examined by molecular dynamics (MD) simulations. Methyl-, ethyl- and butylgroups were adopted as branched chains to distribute along PE backbones. Plastic flow deformation was captured by providing a uniaxial tensile loading at a given strain rate, which shows the characteristic of rate dependence. Current results are in reasonable agreements with existing experimental data. The statistical results show that the longer length of chain branching induces lower equilibrium density and higher yield strength of branched PE. In addition, higher content of chain branching brings higher equilibrium density and lower yield strength of branched PE. It is assumed that the distribution of dihedral angles influences the deformation of PE definitely. The non-bond interactions contribute to the load-bearing capacity of PE largely. Branched PE shows big differences on mechanical behaviours comparing with the linear one. Chain branching distribution also greatly affects the performance of PE, which needs a further discussion. [ABSTRACT FROM AUTHOR]