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The covalently cross‐linked network gives thermosets superior thermal, mechanical, and electrical properties, which, however, squarely makes the large residual stress that is inevitably induced during preparation hardly relieved in the glassy state. In this work, an incredible reduction in residual stress is successfully achieved in bulk thermosets in the glassy state through introducing highly dynamic thiocarbamate bonds by "click" reactions of thiols and isocyanates. Due to the excellent dynamic behaviors of thiocarbamate bonds, local network rearrangement is achieved through thermal stimulation, while the strong 3D cross‐linked network is well maintained. Ultimately, a decrease by 44% in residual stress is detected by simply annealing samples at 30 °C below glass transition temperature (Tg), during which they could well maintain more than 98.4% of the storage modulus. After the annealing, more uniform residual stress distribution is also observed, showing a 32% decline in sample standard deviation. However, the residual stress of epoxy resin, a typical thermoset as a reference, changes little even after annealing at Tg. The results prove it a feasible strategy to reduce residual stress in bulk thermosets in the glassy state by introducing proper dynamic covalent bonds. [ABSTRACT FROM AUTHOR]

The formation of ice on the surface of the metallic casing of high-end equipment poses a potential threat to its operational safety and stability. One important factor that contributes to bonding failure at the ice-metal interface is stress concentration. This paper aims to investigate the effect of stress concentration on the bonding failure behavior at the ice-metal interface through numerical analysis. First, the forms of bonding failure are categorized. Afterwards, the stress distribution state at the corners of the ice-metal interface is determined by the interfacial stress singularity. Finally, numerical analysis is carried out to investigate the thermal stress distribution law at the corners of the interface during the cooling process of the ice-metal bonding, so as to elucidate the induced mechanism of the interfacial stress state on the bonding failure. This study can provide some reference and guidelines for the study of bonding failure at the ice-metal interface. [ABSTRACT FROM AUTHOR]

Cu-catalyzed azide–alkyne cycloaddition (CuAAC) in the case of 1-iodoalkynes is known as a synthetic tool towards 5-iodo-1,2,3-triazole derivatives. We found that CuAAC of 1-iodobuta-1,3-diynes and aryl azides under CuI(PPh3)3 catalysis unexpectedly leads to the formation of both 4-iodo- and 5-iodo-1,2,3-triazoles. Aryl azides bearing acceptor groups and iodoaryldiacetylenes having donor groups shift the isomer ratio in favor of nontrivial 4-iodotriazoles. The reason for the change in the regioselectivity was explained using DFT calculations, which revealed the binuclear nature of the CuAAC transition states (TSs) for iodoalkynes and azides cycloaddition. The regiochemistry of cycloaddition is determined by the type of azide N atom coordinated to the Cu atom and by a spatial arrangement of the binuclear Cu catalyst and alkyne in the TS. In particular in the case of 1-iodobuta-1,3-diynes both regioisomeric TSs have a linear orientation of the alkyne moiety and the I–Cu–P fragment of the binuclear catalyst that makes both N1–Cu (for 5-I-TS) and N3–Cu (for 4-I-TS) coordination possible. The influence of various electronic and stereoelectronic effects established by NBO analysis, as well as NCI interactions, on the stabilization of isomeric TSs in the reactions of aryl/alkyl azides with iodomono- and diacetylenes is discussed. 4-Iodotriazoles are more thermodynamically stable than 5-iodotriazoles, while only the latter form I–N halogen bonds in the solid state. [ABSTRACT FROM AUTHOR]

Two novel cyclic Al3 clusters, Li2[Al3(PR2)6] ⋅ 2(Et2O) [R=Ph (1), Cy (2)] were synthesized through salt metathesis of metastable AlCl ⋅ (Et2O)n solutions with LiPR2. Both complexes were characterized by single crystal X‐Ray diffraction and their solid state and electronic structures are compared to previously reported cyclic Al3 clusters. Compounds 1 and 2 were further characterized using density functional theory (DFT) methods to understand the nature of the free electron and the three‐center two‐electron Al−Al bonds. Calculations revealed that both clusters are influenced by pseudo Jahn‐Teller distortion and are likely in equilibrium between two low energy bonding states. The solid‐state structures of 1 and 2 are unique among Al3 clusters, while the electronic structure is similar to the previously reported [Sit4Al3]. In aluminum chemistry, 1 and 2 are rare examples of clusters containing isoelectronic cores in different ligand environments. The effects of the phosphide ligand sphere and strongly coordinated lithium atoms are discussed in detail. [ABSTRACT FROM AUTHOR]

By combining binding energy and bond‐charge (BBC) model and density functional theory (DFT) calculations, the electrostatic shielding effects and binding energy shifts of bilayer MoS2, MoSe2, and MoTe2 are studied. In this study, the bilayer MoS2, MoSe2, and MoTe2 had bandgaps of 1.38, 1.28, and 1.01 eV, respectively. It is found that electrostatic shielding by electron exchange is the main cause of density fluctuation and determine the bonding state. We found that the edge polarization exactly vanishes after the bulk phase transition, just as we saw the corner‐localized modes disappear in a system with full open boundaries of bilayer MoTe2. Finally, this study establishes a method for calculating the lattice density with Green's function with energy level shift and provides new methods and ideas for the further study of the electrostatic shielding, bond states and topological phases of nanomaterials. [ABSTRACT FROM AUTHOR]

The reactions of zinc(II) bromide with 3- and 4-iodobenzonitriles (3-I-BzCN and 4-I-Bz-CN) afford heteroligand complexes [L2ZnBr2] (L = 3-I-BzCN (I) and 4-I-BzCN (II)), whose structures are determined by X-ray diffraction (XRD) (CIF files CCDC nos. 2253175 (I) and 2253176 (II)). Both crystal structures contain halogen bonds I···Br linking the [ZnBr2L2] fragments into supramolecular layers (I) or chains (II). The energies of these noncovalent interactions are estimated by quantum-chemical calculations. [ABSTRACT FROM AUTHOR]

Silicon dangling bonds (DBs) on an adsorbate-covered Si(100) surface can be created in a scanning tunneling microscope (STM) with high precision required for a number of applications. However, vacancies containing DBs can diffuse, disrupting precisely created structures. In this work, we study the diffusion of Br vacancies on a Si(100)-2 × 1-Br surface in an STM under typical imaging conditions. In agreement with previous work, Br vacancies diffuse at a positive sample bias voltage. Here, we demonstrated that only vacancies containing a positively charged DB hop across the two atoms of a single Si dimer, while vacancies containing neutral and negatively charged DBs do not. Calculations based on density functional theory confirmed that positively charged Br (and Cl) vacancies have a minimum activation barrier. We propose that diffusion operates by both one-electron and two-electron mechanisms depending on the applied voltage. Our results show that the DB charge has a critical effect on the vacancy diffusion. This effect should be taken into account when imaging surface structures with charged DBs as well as when studying the diffusion of other atoms and molecules on the Si(100) surface with vacancies in an adsorbate layer. [ABSTRACT FROM AUTHOR]

This study uses Scholte waves to characterize the interfacial stiffness of a film–substrate structure. A theoretical model was formulated to investigate the dispersion relationships of Scholte waves in immersed film–substrate structures, and simulations of different interfacial states ranging from perfect to weak bonds were performed. The numerical results showed that Scholte waves are sensitive to the variation in the interfacial stiffness, providing the possibility of using the Scholte waves to characterize the bond condition in the film–substrate structure. Experimental tests were conducted on bonded samples under different bond conditions to confirm the theoretical predictions, and the results showed the differences in the dispersion characteristics for different bonding states. The quantification of the interfacial stiffness coefficient between the film and substrate was realized using the inversion method, demonstrating the potential of Scholte waves to evaluate the interfacial properties of a bonded structure. [ABSTRACT FROM AUTHOR]

We extended our studies of the effect of dynamical electron correlation on the covalent bonds in the AH and AF series (A = B–F) to the recoupled pair bonds in the excited a4Σ− states of the CH and CF molecules. Dynamical correlation is energetically less important in the a4Σ− states than in the corresponding X2Π states for both molecules, which is reflected in smaller changes in bond energies (De). Changes in the equilibrium bond distance (Re) and vibrational frequency (ωe), on the other hand, are influenced by the changes in the slope and curvature of the dynamical electron correlation energy as a function of the internuclear distance R, EDEC(R). In the CH(a4Σ−) state, these changes are much smaller than in the CH(X2Π) state, but in the CF(a4Σ−) state, they are larger, reflecting a significant difference in the shapes of EDEC(R) curves. At large R, the shape of EDEC(R) curves for covalent and recoupled pair bonds is similar although different in magnitude. For the CH(a4Σ−) state, EDEC(R) has a minimum at R = Re + 0.72 Å as the orbitals associated with the formation of the recoupled pair bond switch places. EDEC(R) for the CF(a4Σ−) state decreases continuously throughout the bound region of the potential energy curve because the dynamical correlation energy associated with the electrons in the lone pair orbitals is increasing. These results support our earlier conclusion that we still have much to learn about the nature of dynamical electron correlation in molecules. [ABSTRACT FROM AUTHOR]

Boron presents an important role in chemistry, biology, and materials science. Diatomic transition-metal borides (MBs) are the building blocks of many complexes and materials, and they present unique electronic structures with interesting and peculiar properties and a variety of bonding schemes which are analyzed here. In the first part of this paper, we present a review on the available experimental and theoretical studies on the first-row-transition-metal borides, i.e., ScB, TiB, VB, CrB, MnB, FeB, CoB, NiB, CuB, and ZnB; the second-row-transition-metal borides, i.e., YB, ZrB, NbB, MoB, TcB, RuB, RhB, PdB, AgB, and CdB; and the third-row-transition-metal borides, i.e., LaB, HfB, TaB, WB, ReB, OsB, IrB, PtB, AuB, and HgB. Consequently, in the second part, the second- and third-row MBs are studied via DFT calculations using the B3LYP, TPSSh, and MN15 functionals and, in some cases, via multi-reference methods, MRCISD+Q, in conjunction with the aug-cc-pVQZ-PPM/aug-cc-pVQZB basis sets. Specifically, bond distances, dissociation energies, frequencies, dipole moments, and natural NPA charges are reported. Comparisons between MB molecules along the three rows are presented, and their differences and similarities are analyzed. The bonding of the diatomic borides is also described; it is found that, apart from RhB(X1Σ+), which was just recently found to form quadruple bonds, RuB(X2Δ) and TcB(X3Σ−) also form quadruple σ2σ2π2π2 bonds in their X states. Moreover, to fill the gap existing in the current literature, here, we calculate the TcB molecule. [ABSTRACT FROM AUTHOR]

The surprising differences between the experimental solid‐state and calculated gas‐phase structures of 5‐oxo‐1,3,2,4‐dithiadiazole (Roesky's ketone, 1) and 1‐oxo‐1,2,4,3,5‐trithiadiazole (Roesky's sulfoxide, 2), identified and studied in a series of papers published between 2004 and 2010 but then never satisfactorily explained, have been revisited, making use of the more advanced computational possibilities currently available. The previous calculations' considerable overestimations of the C−S and S−S bond lengths in 1 and 2, respectively, have been partly explained based on the results of periodic calculations and the application of Valence Bond (VB) Theory. In the case of 1, the crystal environment appears to stabilize a structure with a highly polarized C=O bond, which features a C−S bond with considerable double‐bond character – an effect which does not exist for the isolated molecule – explaining the much shorter bond in the solid state. For 2, a similar conclusion can be drawn for the S−S distance. For both compounds, though, packing effects are not the sole source of the differences: the inability of Density Functional Theory (DFT) to properly deal with the electronic structures of these apparently simple main‐group systems remains a contributing factor. [ABSTRACT FROM AUTHOR]

In this work, intra- and intermolecular halogen and chalcogen bonds (HlgBs and ChBs, respectively) present in the solid state of nucleic acids (NAs) have been studied at the RI-MP2/def2-TZVP level of theory. To achieve this, a Protein Data Bank (PDB) survey was carried out, revealing a series of structures in which Br/I or S/Se/Te atoms belonging to nucleobases or pentose rings were involved in noncovalent interactions (NCIs) with electron-rich species. The energetics and directionality of these NCIs were rationalized through a computational study, which included the use of Molecular Electrostatic Potential (MEP) surfaces, the Quantum Theory of Atoms in Molecules (QTAIM), and Non Covalent Interaction plot (NCIplot) and Natural Bonding Orbital (NBO) techniques. [ABSTRACT FROM AUTHOR]

The bonding state of the pile-soil interaction is complex. Traditional monitoring methods and tools have not been fully applied to monitor and evaluate it although it affects the lifecycle safety of the pile. In this study, a health monitoring method is proposed to evaluate the bonding state of the pile-soil contact area; it is a transient impact response method based on piezoelectric ceramic sensors to monitor the pile-soil bonding state. During the test, different damage degrees of the pile-soil bonding state were simulated by considering the working conditions of different soil densities and different crack depths as examples. A horizontal transient impact stress was applied to the pile top, and a piezoelectric ceramic sensor embedded in the pile detected the stress wave. As the stress wave response differs in different damage conditions, an energy index was established to quantitatively monitor the degree of damage. [ABSTRACT FROM AUTHOR]

Sydnone methides represent an almost unknown class of mesoionic compounds which possess exocyclic carbon substituents instead of oxygen (sydnones) or nitrogen (sydnone imines) in the 5‐position of a 1,2,3‐oxadiazolium ring. Unsubstituted 4‐positions give rise to the generation of anionic N‐heterocyclic carbenes by deprotonation. Preparations of new sydnone methides are described here. They can be represented by mesomeric structures with either exocyclic carbanionic groups like −C(CN)2−, −C(CN)(COOMe)−, −C(CN)(CONH2)−, and −C(CN)(SO2Me)−, or with the corresponding exocyclic C=C double bonds as a common feature with mesoionic N‐heterocyclic olefins. An X‐ray single structure analysis revealed a length of 140.7(3) pm of the exocyclic bond in the solid state. From the coalescence temperature (55 °C) determined by a series of 13C NMR experiments (150 MHz) at various temperatures, an energy of rotation of 18.5 Kcal/mol was calculated for this bond. The 13C NMR signals of the anionic N‐heterocyclic carbenes, from which the 2‐mesityl‐substituted anionic NHC proved to be stable up to 10 °C, are highly shifted upfield (δcarbene=157.9 ppm−160.5 ppm). The carbenes can be reacted in situ with elemental selenium and chlorophosphanes to yield sydnone methide selenoethers after methylation and 4‐phosphanylsydnone methides in good to excellent yields, respectively. [ABSTRACT FROM AUTHOR]

Many binuclear nickel complexes have NiNi distances suggesting NiNi covalent bonds, including lantern‐type complexes with bridging bidentate ligands. This DFT study treats tetragonal, trigonal, and digonal lantern‐type complexes with the formamidinate, guanidinate, and formate ligands, besides some others. Formal bond orders (ranging from zero to two) are assigned to all the NiNi bonds on the basis of MO occupancy considerations. A VB‐based electron counting approach assigns plausible resonance structures to the dinickel cores. Model tetragonal complexes with the dimethylformamidinate and the dithioformate ligands have singlet ground states whose non‐covalently bonded NiNi distances are close to those in their experimentally known counterparts. Trigonal dinickel complexes are unknown, but are predicted to have quartet ground states with NiNi bonds of order 0.5. The model digonal complexes are predicted to have triplet ground states, but the predicted NiNi bond lengths are longer than those found in their experimentally known counterparts. This could owe to inadequate treatment of electron correlation by DFT in these short NiNi bonds with their multiconfigurational character. All the NiNi bond distances here are categorized into ranges according to the NiNi bond orders of 0, 0.5, 1, 1.5, and 2, no NiNi bonds of order higher than two being identified. The NiNi bonds of given order in these lantern‐type complexes are consistently shorter than the corresponding NiNi bonds in dinickel complexes having carbonyl ligands, attributable to the metalmetal bond lengthening effect of CO ligands. [ABSTRACT FROM AUTHOR]

The electronic structures and contrasting reactivity of [Cu(CF3)4]− and [Cu(CF3)3(CH3)]− were probed using coupled cluster and ab initio valence bond calculations. The Cu–C bonds in these complexes were found to be charge shift bonds. A key finding is that electrostatics likely prevent [Cu(CF3)4]− from accessing a productive transition state for C–C bond formation while promote one for [Cu(CF3)3(CH3)]−. These results therefore highlight essential design criteria for Cu-mediated C–C/C–heteroatom bond formation. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the effect of cold atmospheric plasma (CAP) treatment on resin nanoceramic (RNC) surface state and its bond strength with resin cement. RNC with different surface treatments were prepared: control, sandblasting treatment (SB), hydrofluoric acid etching (HF) and plasma treatment of helium gas (CAP-He) and argon gas (CAP-Ar). The prepared samples were measured by SEM, Ra, Rz, contact angle goniometer, and XPS for surface characteristics. The shear bond test of RNC was examined in nine groups: SB + saline coupling agent (SL), HF + SL, CAP-He/Ar, CAP-He/Ar + SL, SB + CAP-He/Ar + SL, and control. The bond strength between RNC and resin cement was compared using shear bond strength test, before and after thermocycling. After CAP irradiation, the surface topography maintained, while the surface water contact angle was significantly reduced to 10.18° ± 1.36° (CAP-He) and 7.58° ± 1.79° (CAP-Ar). The removal of carbon contamination and inducing of oxygen radicals was detected after CAP treatment. The bond strength was improved by CAP treatment, but varied on CAP gas species and combination methods. CAP of Ar gas had better SBS than He gas. After thermocycling, CAP-Ar + SL showed the maximized shear bond strength (32.38 ± 1.42 MPa), even higher than SB + SL group (30.08 ± 2.80 MPa, p < 0.05). In conclusion, CAP treatment of helium and argon can improve the bonding properties of RNC by improving surface wettability, and CAP of argon gas combined with silane coupling agent shows the highest bond strength. [ABSTRACT FROM AUTHOR]

The chemical debonding energy, initial interfacial frictional bond strength and slip-hardening coefficient between polyvinyl alcohol (PVA) fibres and an engineered cementitious composite (ECC) matrix were obtained by means of single PVA fibre pull-out tests. The effect of three moisture states (fully saturated, semi-saturated and fully dry) on the bonding properties between the PVA fibre and ECC matrix at three target temperatures (25°C, 0°C and −20°C) was investigated. It was found that, at 25°C, the bonding properties decreased with an increase in moisture content. At 0°C and −20°C, the bonding properties increased with an increase in moisture content. At −20°C in the fully saturated state, the bonding load was too large to cause fibre rupture. The bonding properties were found to increase with decreasing temperature in the fully saturated and semi-saturated states and decrease with decreasing temperature in the fully dry state. This study of the effect of low temperature and moisture state on the bonding properties between PVA fibres and ECCs provides theoretical support for how to ensure good ductility when ECCs are in service at low temperature. [ABSTRACT FROM AUTHOR]

In this work, we proposed a two-phase hydrothermal synthesis approach to fabricate high-curvature bulk surface with engineered in-plane defects. Organic or supercritical solvents were introduced as a second immiscible media to alter MoS 2 hydrothermal growth. Two mixing scenarios, depending on the ratio of organic solvent to aqueous solution. In the case of the organic solvent isolated by aqueous solution, the growing slabs change its original direction when getting contact with the organic droplets. In the scenario that aqueous droplets dispersed in organic solvent, MoS 2 slabs grow along the curved interfaces of aqueous droplets. Experimental results showed that the curved basal planes were generated in the two cases and more curvatures were introduced in the second phase under adequate mixing energy. Higher curvature degree led to a better catalytic performance. Compared to decalin, supercritical heptane that can facilitate the dispersion of the precursor-containing aqueous solution into homogeneous nano-size reaction cells, showed a great capacity to generate highly curved slabs. MoS 2 synthesized with supercritical solvent exhibits the highest activity among the investigated catalysts. The catalysts were characterized by SEM, XRD, XAFS, TPR and nitrogen adsorption analysis. The results were proved by the theoretical calculations that the formation energy (E form) of sulfur vacancy (V S) on curly structure possesses a reduction of 0.19 eV comparing with planar MoS 2 monolayer. The curved structure can facilitate the surface V S generation by depopulating the occupied bonding states of corresponding Mo-S bonds. This work provides an effective approach to create basal defects on the MoS 2 to promote its catalyst activity. [Display omitted] • In-plane defects were fabricated by a novel two-phase hydrothermal synthesis. • More defects (curvatures) are created when organic solvent is in majority. • Compared to organic solvent, supercritical solvent generates more curly structure. • The formation energy of sulfur vacancy on curly structure is lower than planar MoS 2. • MoS 2 synthesized with supercritical solvent exhibits the highest activity. [ABSTRACT FROM AUTHOR]

The trapping reactions of carbene analogs G14F2 (G14 = group 14 element) by the benzene‐bridged B/P‐Rea frustrated Lewis pair (FLPs) molecule are studied using density functional theory (B3LYP‐D3(BJ)/def2‐TZVP). Our theoretical investigations predict that only the CF2 intermediate rather than other heavy carbene analogs can be trapped by the B/P‐Rea FLP‐type molecule. Energy decomposition analysis‐natural orbitals for chemical valence (EDA‐NOCV) analyses indicate that the bonding nature of the G14F2 catching reactions by the B/P‐Rea FLP‐type molecule is a donor–acceptor (singlet–singlet) interaction rather than an electron‐sharing (triplet–triplet) interaction. Moreover, EDA‐NOCV and frontier molecular orbital (FMO) theory findings strongly suggest that the lone pair (LP) (P) → vacant p–π‐orbital (G14F2) interaction rather than the empty σ‐orbital (B) ← sp2‐σ‐orbital (G14F2) interaction plays a predominant role in establishing its bonding condition during the G14F2 trapping reaction with the B/P‐Rea FLP‐associated molecule. Our activation strain model findings reveal that the atomic radius of the G14 element of G14F2 plays a key role in determining the activation barrier of the G14F2 trapping reactions by the benzene‐bridged B/P‐Rea FLP. The valence bond state correlation diagram (VBSCD) model developed by Shaik is used to rationalize the calculated results. The VBSCD findings demonstrate that in the present trapping reactions, the singlet triplet splitting of G14F2 plays a significant role in influencing its reaction barrier and reaction enthalpy. Our theoretical results demonstrate that the relationship between the geometrical parameters of the transition states and the corresponding reaction free energy barriers agrees well with the findings based on the Hammond postulate. [ABSTRACT FROM AUTHOR]

While it is prominent for governments across the globe to promote charitable giving, few governments directly intervene in charitable fundraising due to ethical and political risks. An exception is the Chinese government that has actively sought private donations. Using a national dataset of Chinese giving, this study explores from a general political participation perspective how individuals responded to different levels of state intervention in private charity. It finds that people made (a) voluntary donations (little state intervention) in relation to their social involvement and civic engagement, (b) suggested donations (e.g., the state called for donations) in relation to their civic participation and formal political participation, and (c) coerced donations (e.g., the state demanded donations) in relation to their personal bonds with the state. Thus, while appropriate state intervention seems productive, undue intervention may damage both charity and state legitimacy. Implications and suggestions for future research are included. [ABSTRACT FROM AUTHOR]

We prove the statement in the title for a suitable (wavefunction-dependent) choice of the underlying orbitals and show that 3 is optimal. Thus, for two-electron systems, the quantum chemistry density matrix renormalization group (QC-DMRG) method with bond dimension 3 combined with fermionic mode optimization exactly recovers the full configuration-interaction (FCI) energy. [ABSTRACT FROM AUTHOR]

Diffusion bonding is a joining process that relies on the inter-diffusion of atoms across the interface as the primary mechanism. Diffusion bonding techniques such as solid state and transient liquid phase (TLP) bonding are currently performed in a vacuum, which is a time-consuming, costly method and also limits the size of the components that can be bonded adequately. The present study aims at achieving the diffusion bonded joints of AA2014 under the bonding temperatures of 440, 460, and 480 0C. Microstructural evaluation is carried out using light optical microscopy (LOM), and scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) is used for elemental analysis on the interface of the bonded specimens. Hardness at the interface is evaluated using the Vickers Microhardness test. [ABSTRACT FROM AUTHOR]

Photoinduced phase transition (PIPT) is always treated as a coherent process, but ultrafast disordering in PIPT is observed in recent experiments. Utilizing the real-time timedependent density functional theory method, here we track the motion of individual vanadium (V) ions during PIPT in VO2 and uncover that their coherent or disordered dynamics can be manipulated by tuning the laser fluence.We find that the photoexcited holes generate a force on each V–V dimer to drive their collective coherent motion, in competing with the thermal-induced vibrations. If the laser fluence is so weak that the photoexcited hole density is too low to drive the phase transition alone, the PIPT is a disordered process due to the interference of thermal phonons. We also reveal that the photoexcited holes populated by the V–V dimerized bonding states will become saturated if the laser fluence is too strong, limiting the timescale of photoinduced phase transition. [ABSTRACT FROM AUTHOR]

The article aims at understanding what sanctions and military assistance to Ukraine can and cannot accomplish to halt Russian aggression. It mentions investment has dried up, imports have dropped, inflation is rising, markets have closed, and Russian state bonds have been downgraded to junk status, and freezing of financial assets and the embargo on strategic imports are generating unemployment and inflation that cause harm for people.

[Display omitted] • The surface phosphorus-induced strategy generates Ni-P(δ−) and Fe-P(δ−) stable bonding states. • The recombination of photoinduced electron-hole pairs was inhibited. • Enhanced absorbance intensity and absorption range. • Hydrogen evolution performance is 82 times of the NiFe-LDH. Light-driven semiconductor splitting of water for hydrogen production is becoming increasingly important in the direction of obtaining clean energy. In this study, high-temperature P-induced corrosion of NiFe-LDH was used to generate P-metal strong surface bonding states. The surface layout of Ni/Fe-P(δ−) covalent bonds on the one hand enriches the active sites for photocatalytic hydrogen evolution and opens up the valve for accelerated hydrogen production. On the other hand, it opens the migration channel for photogenerated electrons, which broadens the electron supply for photocatalytic hydrogen generation. FTIR spectroscopy and XPS results showed that Ni/Fe-P covalent bonds were successfully deployed on the catalysts. PL results showed that the introduction of covalent bonds had a facilitating effect on promoting the separation and migration of photogenerated electrons. The design of Ni-P(δ−) and Fe-P(δ−) bonds was further confirmed by In situ irradiated X-ray Photoelectron Spectroscopy to open the channels for trapping and transporting electrons. Based on the experimental results, we propose a possible bimolecular mechanism for synergistic hydrogen evolution, which provides novel and unique insights into the in-depth analysis of the influence of surface bonding states on the photocatalytic mechanism. [ABSTRACT FROM AUTHOR]

Front Cover: Residual stresses in thermosets are hardly relieved in the glassy state. In article 2300735, however, Kangning Wu, Chenhui Cui, Jianying Li, and co‐workers demonstrate incredible residual stress reduction in polythiourethane incorporated with dynamic covalent bonds by simply annealing below the glass transition temperature (Tg), during which excellent properties gifted by the highly cross‐linked network of thermosets are well maintained..By Kangning Wu; Dongxu An; Zhuolin Zhang; Ge Zhao; Chenhui Cui; Fusheng Zhou and Jianying LiReported by Author; Author; Author; Author; Author; Author; Author [Extracted from the article]

Herein we describe a designed protein building block whose self-assembly behaviour is dually gated by the redox state of disulphide bonds and the identity of exogenous metal ions. This protein construct is shown – through extensive structural and biophysical characterization – to access five distinct oligomeric states, exemplifying how the complex interplay between hydrophobic, metal–ligand, and reversible covalent interactions could be harnessed to obtain multiple, responsive protein architectures from a single building block. [ABSTRACT FROM AUTHOR]

Layered rock mass generally has adverse effects on the seismic stability of deep-buried underground powerhouses. Aiming at the complexity of seismic wave field in deep-buried underground powerhouses, the obliquely input methods of P and SV waves considering the incident direction and multi-incident surfaces are constructed in this study, respectively. It can convert the seismic wave input problem into the problem of solving equivalent nodal force acting on the artificial boundaries. Based on the characteristics of dynamic interaction between interlayers in layered rock mass, an explicit dynamic contact force method considering the seismic deterioration effect and bond-slip characteristics of interface is also presented to simulate various contact states such as bond, separation, and sliding. The combined application of the above methods to analyze the seismic response of underground powerhouse at Azad Pattan hydropower station shows that they could accurately simulate the seismic damage evolution process of deep-buried underground powerhouses in layered rock mass. The numerical results indicate that the obliquely incident seismic waves contribute to a larger seismic reaction of underground powerhouses, which largely lies in the amplitudes of the displacement and stress fluctuations. After considering the dynamic contact, the obvious seismic deterioration effect and interlaminar dislocation displacement occur between soft and hard rock, and the sidewalls suffer more severe deterioration degree than the top arch. The seismic damage area of lining structure is mainly distributed in the place where the soft rock strata pass through and the upper structure with larger free surface. Additionally, two major damage modes of underground powerhouses in layered rock mass, namely, damage due to structural deformation and interlaminar dislocation, are derived from the numerical results and can be reasonably explained by the corresponding damage mechanisms. [ABSTRACT FROM AUTHOR]

The recently conceived gap test and its simulation revealed that the fracture energy Gf (or Kc, Jcr) of concrete, plastic-hardening metals, composites, and probably most materials can change by ±100%, depending on the crack-parallel stresses σxx, σzz, and their history. Therefore, one must consider not only a finite length but also a finite width of the fracture process zone, along with its tensorial damage behavior. The data from this test, along with ten other classical tests important for fracture problems (nine on concrete, one on sandstone), are optimally fitted to evaluate the performance of the state-of-art phase-field, peridynamic, and crack band models. Thanks to its realistic boundary and crack-face conditions as well as its tensorial nature, the crack band model, combined with the microplane damage constitutive law in its latest version M7, is found to fit all data well. On the contrary, the phase-field models perform poorly. Peridynamic models (both bond based and state based) perform even worse. The recent correction in the bond-associated deformation gradient helps to improve the predictions in some experiments, but not all. This confirms the previous strictly theoretical critique (JAM 2016), which showed that peridynamics of all kinds suffers from several conceptual faults: (1) It implies a lattice microstructure; (2) its particle-skipping interactions are a fiction; (4) it ignores shear-resisted particle rotations (which are what lends the lattice discrete particle model (LDPM) its superior performance); (3) its representation of the boundaries, especially the crack and fracture process zone faces, is physically unrealistic; and (5) it cannot reproduce the transitional size effect--a quintessential characteristic of quasibrittleness. The misleading practice of "verifying" a model with only one or two simple tests matchable by many different models, or showcasing an ad hoc improvement for one type of test while ignoring misfits of others, is pointed out. In closing, the ubiquity of crack-parallel stresses in practical problems of concrete, shale, fiber composites, plastic-hardening metals, and materials on submicrometer scale is emphasized. [ABSTRACT FROM AUTHOR]

The ability to control molecular-scale motion using electrostatic interactions was demonstrated using an N-phenylsuccinimide molecular rotor with an electrostatic pyridyl-gate. Protonation of the pyridal-gate forms stabilizing electrostatic interactions in the transition state of the bond rotation process that lowers the rotational barrier and increases the rate of rotation by two orders of magnitude. Molecular modeling and energy decomposition analysis confirm the dominant role of attractive electrostatic interactions in lowering the bond rotation transition state. [ABSTRACT FROM AUTHOR]

The (0001) surface band structure evolution of Bi2Se3 is studied for different broken symmetries in the top quintuple layer (QL) of 8QLs slab. Each surface electronic structure shows dangling bond states (DBS) irrespective of broken symmetries introduced by the surface termination or layer vacancy. The DBS become topological (TDBS) in the presence of spin–orbit coupling (SOC) effect, which form multiple Dirac cones (DC) at the Γ and M points in the conduction band due to Bi1 termination in top QL. For Bi1 and Se2 terminations, the contribution of p‐orbital of Bi2 atom to DBS in the gap is negligible. The DBS eliminates the topological state of Bi2Se3 for all broken symmetries except Se2 layer vacancy. The band structure with only Se2 and Se3 layer vacancies shows a narrow‐bandgap semiconducting nature with a small bandgap value of 0.18 eV and 0.08 eV, respectively. The DC feature is observed in vacant atomic layer configurations with SOC. The layer vacancies created by Bi atoms form a metallic state, whereas those produced by Se atoms form a narrow‐bandgap semiconducting state. The introduction of broken symmetries in Bi2Se3 can be utilized in the tuning of surface states and TDBS for possible technological applications. [ABSTRACT FROM AUTHOR]

Based on the actual packaging structure of insulated gate bipolar transistor (IGBT) module, this article establishes the power loss model, and analyzes the influence of the position of the lift-off bond wire on the module. Through the theoretical analysis, it is found that the position of the lift-off bond wire is an important factor affecting the aging of the modules. And then the electrothermal coupling model of IGBT is established for simulation, and an experimental platform is built for verification. The results show that the distribution of bond wire lift-off position is one of the characteristics of bond wire failure. When the bond wire lift-off failure is concentrated on a single IGBT chip, it will accelerate the aging process of the modules. Therefore, this article considers that the position of the lift-off bond wire is a significant factor in the aging process of the modules, which should be fully considered in the bond wire state evaluation. In addition, the research results of this article can also provide theoretical reference for the optimization of IGBT module packaging structure. [ABSTRACT FROM AUTHOR]

[Display omitted] • A rare example of a square-planar silver(I) tetratriflate complex was structurally characterized. • Halogen bonds in the solid state have been discovered and described. • Calculations were employed to optimize the geometry of the [Ag(OTf) 4 ]3– anion in the gas phase. In this work, we have experimentally and theoretically shown that halogen bonding can stabilize the rare example of square-planar configuration of the silver(I) center. The crystallographic analysis of tris -dibenziodolium silver(I) tetratriflate reveals two types of halogen bonding interactions between the triflate ligands and the dibenziodolium cation, which might stabilize the such square-planar coordination geometry. Theoretical calculations confirm the noncovalent nature of the I⋅⋅⋅O contacts and provide insights into their electronic properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • We have provided clear evidences for the covalent nature of H-bonding interactions in the 2D ice. The uniqueness of all H-bonds in 2D ice lies in the fact that their energies are populated at specific levels, which is fundamentally different from conventional H-bonds in liquid water and water ice. All H-bonds are composed of several different covalent bonding and antibonding states. • The covalent H-bonding interactions are evidenced by the hydrogen intensities in the three-body H-bonding interactions. The covalent interactions of the 1b 2 orbitals are evidenced in the asymmetrically H-bonded cyclic motif, while the symmetrically H-bonded cyclic motif finds the covalent evidences from the 3a 1 orbitals. In particular, the covalent bonding states consisting of pure 1b 2 orbitals strengthen the asymmetrically H-bonded cyclic motif, while the covalent bonding states consisting of pure 3a 1 orbitals strengthen the symmetrically H-bonded cyclic motif. • We have provided clear evidences for the electrostatic nature of H-bonding interactions in the 2D ice. As the vertical waters in asymmetrically H-bonded cyclic motif act as the proton donors when forming interlayer H-bonds, the polarization of OH dipoles along the vertical direction is enhanced. As the vertical water act as the proton acceptors when forming intralayer H-bonds, the oxygen atoms in the horizontal direction exhibit depleted charge density. • The vertical waters in the symmetrically H-bonded cyclic motif always acts as the proton donors, and the OH dipole polarization is enhanced in both the formation of interlayer and intralayer H-bonds, while the internal polarization of the flat-lying water is weakened, which leads to the electrostatic interactions of all H-bonds in both H-bonded cyclic motif exhibiting alternating charge gain and loss states along the proton transfer direction. This is a typical evidence for the electrostatic cooperation of all H-bonding interactions in 2D ice. • The inner water molecule has more charge gain and loss with the metal, indicating that the inner H-bond has more electrostatic interactions than the outer H-bond. These findings significantly advance our understanding on the H-bonding nature in the 2D ices, and they may also have rich implications to fundamental processes in interfacial waters on metal electrodes. Using density functional theory calculations, we provided clear evidence for the covalent and electrostatic nature of rich H-bonds in the 2D ice. Interestingly, we find that all H-bonds consistently populate several different principal states with both the bonding and antibonding features. However, the symmetric and asymmetric H-bonded cycles respectively show preferential HOMO-1 (3a 1) and HOMO-2 (1b 2) contributions to the H-bonding states. For all H-bonding types, alternating positive and negative regions on the second order serve as the direct evidences for the H-bonding electrostatics. Our investigations advance our understanding of the H-bonding nature of rich H-bonds in the ice. [ABSTRACT FROM AUTHOR]

The recent discovery of Leidenfrost droplet trampolining deviates from the traditionally accepted steady-state assumption and updates our understanding of Leidenfrost droplet state. However, the conditions of trampolining and its effect on heat transfer have not been fully understood. To address these issues, this study numerically investigates the dynamic behavior and heat transfer characteristics of Leidenfrost droplets under varying liquid viscosity and droplet size. A regime map for Leidenfrost droplet state with respect to Bond number and Ohnesorge is presented. Particularly, an unreported oscillation regime is discovered between equilibrium regime and trampolining regime. The results indicate that low viscosity and moderate droplet size favor the observation of trampolining. Besides, the oscillating droplet is modeled via a mass-spring-damper system in both equilibrium and oscillation regimes, with damping coefficient, spring constant and oscillation period quantitatively correlated with liquid viscosity and droplet size by simple scaling laws. In the trampolining regime, an intriguing phenomenon is observed as the maximum vapor layer thickness demonstrates two local maxima with increasing droplet size. We also quantitatively unravel that reducing liquid viscosity and increasing droplet size can lead to a thicker vapor layer thickness, thus inhibiting the heat transfer to the droplet. [ABSTRACT FROM AUTHOR]

• TM-DHPD is proposed to address thermally induced crack propagation problems. • It takes both advantages of DHPD and peridynamic correspondence model. • The interface bond damage model is proposed for heterogeneous materials. • Linearizations of TM-DHPD in the context of peridynamics are firstly derived. • It can naturally capture crack branching, kinking and interfacial de-bonding. To accurately address the thermally induced dynamic and steady-state crack propagation problems for homogeneous and heterogeneous materials involving crack branching, interfacial de-bonding and crack kinking, we propose the fully coupled thermo-mechanical dual-horizon peridynamic correspondence damage model (TM-DHPD). To this end, the integral coupled equations for TM-DHPD are firstly derived within the framework of thermodynamics. And then, the alternative dual-horizon peridynamic correspondence principle is used to derive the constitutive bond force state, heat flow state and their general linearizations. Moreover, the unified criterion for bond damage is proposed to characterize the internal bond damage in a single material and the interface bond damage in dissimilar materials. To ensure convergence and accuracy, the coupled equations are solved using the standard implicit method without the use of artificial damping. In both homogeneous and heterogeneous materials, some representative and challenging numerical cases are examined, such as dynamic crack branching in a centrally heated disk and multiple interface failure of thermal barrier coating. The numerical results are in good agreement with the available experimental results or the previous predictions, which shows the great potential of the proposed TM-DHPD in addressing the physics of numerous thermally induced fractures in the real-world engineering problems. [ABSTRACT FROM AUTHOR]

Unsaturated soil-continuum interfaces determine the behavior of structures such as friction piles embedded in unsaturated soil and retaining walls with unsaturated backfill. Developing accurate constitutive models for these interfaces is essential for innovative computational design and analysis in geotechnical engineering. This study presents a rigorous mathematical derivation to quantify the bonding effect at interparticle and pore space contact zones, introducing a bonding variable and a state parameter based on the ratio between current and critical void ratios. The novelty lies in introduction of a hydraulic-mechanical (HM) coupling constitutive model for unsaturated soil-continuum interfaces, incorporating the bonding effect and critical-state concept. Despite the 16 parameters in proposed model, all are methodically calibrated using suction-controlled interface shear tests. Effectiveness of the model is demonstrated through predictions in interface shear tests involving unsaturated Toyoura sand, smooth/rough steel, and published tests with unsaturated Minco silt and steel. The model's applicability is extended to diverse conditions, including structural stiffness, interface thickness, counterface roughness, and drying- wetting (D-W) cycles. This model provides a unified framework for analyzing volume changes and stress-displacement responses in unsaturated soil-continuum interfaces, providing valuable insights for design of pile foundations in unsaturated soils. [ABSTRACT FROM AUTHOR]

[Display omitted] • Zinc(II) complexes featuring 2,1,3-benzoselenadiazole ligands were synthesized and structurally characterized. • Chalcogen bonds in the solid state have been discovered and described. • The catalytic activity of these complexes was studied in the model reaction of the Schiff condensation. XRD study of crystals of zinc(II) halide complexes featuring 2,1,3-benzoselenadiazole (L) ligands [Zn L 2 X 2 ] (X = Cl, Br, I) indicated availability of intramolecular chalcogen bonds between the Se atom and the halide ligands, which affect a rotation barrier around the Zn–N bonds and thus control a geometry of these species. In the solid state, the Se atom additionally forms intermolecular chalcogen bonds with the N atom of the 2,1,3-benzoselenadiazole ligands, which results in formation of infinite 1D chains. Theoretical calculations and experimental kinetic study indicated that although the Se atom serves as a Lewis acid, coordination of the organic ligand to the zinc(II) center does not provide enhanced catalytic activity of the latter in the model reaction of the Schiff condensation. [ABSTRACT FROM AUTHOR]

Bio-based hydrogels formed by the chemically or physically cross-links are promising materials in the biological system. In this paper, we propose a constitutive model within the framework of finite-strain viscoelasticity to investigate the mechanical behaviors of bio-based polyelectrolyte complex (PEC) hydrogels from the ionic complexation of sodium hyaluronate (HA)/chitosan with and without chemical crosslinkers. The structure of the viscoelastic constitutive model consists of a spring and a Kelvin element, in which two softening factors are adopted to represent the states of ionic bonds and bridges in the hydrogels. Based on some constitutive assumptions and through the conventional approach of thermodynamics, the constitutive equation system of the model is derived. Corresponding to the hydrogels with different crosslinker concentrations, the values of material parameters in the model are identified. To show the validity of the model, it is applied to simulate the mechanical behaviors of the hydrogel samples in the uniaxial tensile tests and cyclic loading–unloading tests. It is found that the model predictions can fit the experimental data quite well. Based on the modeling results, some further analyses regarding the effects of softening factors on the response of HA/chitosan hydrogels have also been conducted. • A viscoelastic model is proposed to study the mechanical behaviors of PEC hydrogels. • Two softening factors are adopted to represent the states of ionic bonds and bridges. • Parameters are identified for hydrogels with different crosslinker concentrations. • The mechanical response of PEC hydrogels can be predicted accurately by the model. • The effects of softening factors on the response of PEC hydrogels are analyzed. [ABSTRACT FROM AUTHOR]

• A peridynamics-based framework is established for elastic-plastic ductile fracture problems. • Energy dissipation rate-based bond failure criterion is proposed for ductile crack growth modeling. • The peridynamic models successfully capture the characteristics of elastic-plastic deformation and ductile fracture. A peridynamics-based framework is established for the elastic-plastic ductile fracture analysis. In this frame, a new state-based peridynamic elastic-plastic model is presented using the novel bond extension state forms of yield function and plastic flow rule. The nonlinear energy release rate is computed by the extended peridynamic finite crack extension (PFCE) method, and an energy dissipation rate-based bond failure criterion is proposed for ductile crack growth modeling. Numerical methods for plastic states update and yield function solution are also given. Then, examples of plates with a center hole or a center crack, and compact tension (CT) tests are analyzed by the proposed models, and compared to those from theoretical and FEM solutions. The results demonstrate that the proposed peridynamic models can well capture the characteristics of elastic-plastic deformation and ductile fracture, including the plastic shape and size, energy distributions, nonlinear energy release rate, load-displacement and resistance curves, etc. [ABSTRACT FROM AUTHOR]

The redox non-innocent ligand bis(o -aminophenol) N,N′-bis(3,5-di-tertbutyl-2-hydroxy-phenyl)-1,2-phenylenediamine and CoCl 2 ⋅6H 2 O react in a methanol solution under aerobic conditions to form a paramagnetic Co(III) complex. [Display omitted] • Low-spin Co(III) complex with a redox non-innocent ligand. • Paramagnetic complex with an unpaired electron on the ligand. • Metrical oxidation state and bond valence sum calculations verify the + III oxidation state. The redox non-innocent ligand bis(o -aminophenol) N,N′-bis(3,5-di-tertbutyl-2-hydroxy-phenyl)-1,2-phenylenediamine, H 4 L, reacts with CoCl 2 ⋅6H 2 O in a methanol solution under aerobic conditions to form [Co(HL) 2 ]. Both bis(o -aminophenol) ligands coordinate as tridentate and the ligand set can be described as a resonance structure of two partially oxidized ligands, while the formal oxidation state of the metal centre appears as + III. In this resonance structure, one ligand carries an odd electron, which makes the Co(III) complex paramagnetic. [ABSTRACT FROM AUTHOR]

• Three-point bending tests on BFRP- and CFRP - strengthened reinforced concrete beams were revelated. • Distributed fibre optic sensing was used to measurement of strain in steel- and FRP-reinforcement. • The experimental results show brittle debond failure of BFRP and CFRP strips. • The analytical investigation allows to conclude the ultimate state of maximal bond forces on intermediate crack elements. Recently, the implementation of strengthening systems for concrete structures as externally bonded carbon fibre-reinforced polymer (EBR-CFRP) has been used more frequently than the system with an externally bonded basalt fibre-reinforced polymer (EBR-BFRP). Through many years of an international investigation, a safe design model for CFRP strips has been developed, unfortunately, it could not be used for the calculation of reinforced concrete strengthened by lower stiffness strips such as BFRP, without previous validation. The differences appear in the bond shear stress – slip relationship, which is required for a more accurate design. The research on bending behaviour of strengthened concrete structures is necessary to offer a practical engineering and design model for a new retrofitting system. This paper presents the analytical evaluation of externally bonded BFRP and CFRP strips on the load-bearing behaviour of reinforced concrete structures and its verification on the experimental results. The validity of this study was completed based on the basis of the strain measurement of steel- and FRP-reinforcement using distributed fibre optic sensing. [ABSTRACT FROM AUTHOR]

The non-linear threshold-type current-voltage behavior that characterizes selector devices for three-dimensional (3D) crossbar-type nonvolatile memory devices relies upon a phenomenon known as Ovonic threshold switching (OTS). Because current practical OTS materials are based on toxic elements, such as Se and As, Te-based OTS materials are expected to offer a more environmentally friendly option. However, the electronic structure that determines the OTS behavior of Te-based OTS materials is not well understood. In this paper, the electronic structure of amorphous Si 0.29 Te 0.71 , has been explored using hard X-ray photoelectron spectroscopy (HAXPES) in conjunction with density functional theory (DFT) calculations. The HAXPES results show that the Si 0.29 Te 0.71 amorphous network of the simulated amorphous structure is based upon Te-Te, Te-Si, and Si-Si bonding. DFT calculations revealed that Si3p and Te5p states contribute to bonding, whereas occupied non-bonding Te5p states form the top of the valence state. A projected local density of states analysis shows that the Si site forms conduction-tail states, whereas the Te site forms both conduction- and valence-tail states. Furthermore, Te-Te dimers contribute significantly to the midgap states that characterize the OTS behavior. Finally, the valence-tail state extension within the mobility gap of Si 0.29 Te 0.71 was experimentally demonstrated. [Display omitted] [ABSTRACT FROM AUTHOR]

This DFT study on model vanadium-nickel lantern-type complexes predicts that (1) digonal complexes have quartet ground states with V-Ni bonds of bond order 1.5, (2) trigonal complexes have quintet ground states with long V-Ni separations, and (3) tetragonal complexes have doublet ground states with V-Ni bonds of bond order 1.5. [Display omitted] • Three series of vanadium-nickel lantern-type complexes VNiL x (x = 2, 3, 4; L = bidentate bridging ligand) are studied here by DFT using the MN15-L functional. • Digonal complexes VNiL 2 have quartet ground states with V-Ni bonds of order 1.5. • Trigonal complexes VNiL3 have quintet ground states with long V-Ni separations. • Tetragonal complexes VNiL 4 have doublet ground states with V-Ni bonds of bond order 1.5. • Various criteria for V-Ni bond strength are estimated, compared with one another, and categorized into ranges according to V-Ni bond orders from zero to two. Heterobinuclear complexes with metal–metal bonds have been increasingly studied over the past two decades. Binuclear vanadium-nickel lantern-type complexes are studied here by density functional theory using the MN15-L functional. Three series of digonal, trigonal, and tetragonal lantern-type complexes VNiL x (x = 2, 3, 4) are treated, where the ligand L is formamidinate (fad), guanidinate (gua) and formate (OCHO). A trigonal complex with phosphinoamide ligands is also treated. Each complex is treated in three low-lying spin states to predict the ground state spin multiplicity. The V-Ni bond lengths obtained are noted with reference to the metal–metal formal bond order (fBO) values derived from molecular orbital analysis. Electron-bookkeeping diagrams derived from an electron counting strategy also yield V-Ni formal bond order values consistent with the V-Ni bond lengths and with the fBO values from MO analysis. The four ligands studied are compared with regard to their effects upon metal–metal bonding. The V-Ni bond lengths in these complexes, along with the V-Ni bond stretching frequencies, Wiberg bond index and formal shortness ratio values, are all categorized into ranges according to the V-Ni bond orders from zero to two. [ABSTRACT FROM AUTHOR]

Adhesive bonding is widely used for joining light weight structures and surface preparation methods play a significant role in improving the bonding quality. Bond quality assessment of thermoplastic composites can be challenging due to the highly inhomogeneous structure. This article explores the use of ultrasonic testing to nondestructively characterize the bond state between thermoplastic composites with different surface preparation methods. Classification of bond states was carried out using a physics-based statistical method and machine learning based method. The results suggest that machine learning methods show a higher classification accuracy. The ultrasonics results were validated using destructive lap-shear testing. [ABSTRACT FROM AUTHOR]

In this study, a cohesive strengthening/damage-plasticity model (CS/DPM) based on the discrete element method (DEM) was proposed to better simulate the hardening/softening effect and shear dilatancy/shrinkage characteristic of rock and soil. Firstly, on the basis of the original cohesive damage-plasticity model (CDPM), a cumulative strengthening variable was defined to characterize the evolution of bonded contact stiffness and strength with plastic strain at the grain scale. According to the hyperbolic yield criterion, the critical stress state of the bond during the transition from elastic to plastic was determined. The strengthening and damage thresholds were introduced separately to control the extent of hardening and softening. On this basis, the shear shrinkage effect between particles was considered and incorporated into the development of the constitutive model algorithm as a stress return mechanism. Subsequently, a series of simulation experiments were carried out and the results were compared with the existing experimental or numerical solutions to verify the correctness and feasibility of the model. In addition, the impact of different contact parameters on the mechanical response was analyzed in a comparative manner to provide a reference for studying the hardening/softening behavior and failure mechanism of rock and soil from the mesoscopic scale. [ABSTRACT FROM AUTHOR]

By performing first principles calculations, we investigate the edge reconstruction in free-standing 2D-Xene (X = Si, Ge, Sn) zigzag nanoribbons. Three different periodicities of edge reconstruction (2 a , 3 a , 4 a) are found, in which the reconstruction with 3 a periodicity has the lowest energy and shows non-magnetic ground state. The edge reconstruction can be understood by the reconfiguration of the dangling bond states and edge states at the zigzag edges. Due to the structural buckling, extra bonding states are formed between edge atoms and inner atoms, accompanied with charge transfer from the edge states to the dangling bond states. This results in one-third occupied dangling bond states and a Peierls-like structural reconstruction with 3 a periodicity at the edge which opens a small band gap. With a tight binding model, the reconstruction of the electronic structures at the edges are revealed by the hopping integrals between different edge X-p orbitals. • 2D Xene edge buckling leads to charge transfer from edge states to dangling bond states • 3a edge reconstruction originates from the 1/3 band filling of dangling bond states • Tight binding model reveals the charge transfer and bonding interactions at the edge [ABSTRACT FROM AUTHOR]

[Display omitted] • We developed time-dependent Hartree-Fock-Bogoliubov (TDHFB) method, a simple excited-state method with static correlation. • We employed the canonical-basis (Cb-)TDHFB formulation to avoid the violation of the electron number preservation. • The real-time Cb-TDHFB method can describe a multi-configurational character in excited states of bond dissociation. The Hartree–Fock–Bogoliubov (HFB) method, an efficient way to treat static electron correlations, has been applied to molecular systems in the ground state. In this letter, we propose a time-dependent (TD) HFB method for treating the excited states of molecules with static correlations at a reasonable computational cost. To avoid electron number violations, we also consider the canonical basis variant of the TDHFB method proposed by Ebata et al. Results of calculations for the elongated hydrogen molecule reveal that the TDHFB method can partially incorporate two-electron excited determinants. [ABSTRACT FROM AUTHOR]