Deformation Energy Research Articles

Understanding the Reactivity of "Naked" Acyclic Carbene-like Species Featuring a Group 13 Element in the [4+1] Cycloaddition with Benzene.

The chemical reactivity between benzene and the "naked" acyclic carbene-like (G13X2)- species, having two bulky N-heterocyclic boryloxy ligands at the Group 13 center, was theoretically assessed using density functional theory computations. Our theoretical studies show that (BX2)- preferentially undergoes C-H bond insertion with benzene, both kinetically and thermodynamically, whereas the (AlX2)- analogue favors a reversible [4 + 1] cycloaddition. Conversely, the heavier carbene analogues ((GaX2)-, (InX2)-, and (TlX2)-) are not expected to engage in a reaction with benzene. The activation strain model analysis suggests that the geometric deformation energy of benzene, driven by the relativistic effects of the central G13 element in the (G13X2)- molecule, is crucial in determining the chemical reactivity of the [4 + 1] cycloaddition with benzene. According to our theoretical analyses, the stronger forward bonding is specifically the sp2-σ-orbital (G13) → vacant protruding p-π* orbitals (bent benzene). In contrast, the weaker backward bonding is the empty p-π orbital (G13) ←-filled protruding p-π orbital (bent benzene). Moreover, our theoretical findings indicate that the singlet-triplet splitting of (G13X2)- can be used as a diagnostic measure to predict the barrier height and reaction energy for their [4 + 1] cycloaddition with benzene.

Ligand-Induced Activation of Single-Atom Palladium Heterogeneous Catalysts for Cross-Coupling Reactions.

Single-atom heterogeneous catalysts (SACs) are potential, recoverable alternatives to soluble organometallic complexes for cross-coupling reactions in fine-chemical synthesis. When developing SACs for these applications, it is often expected that the need for ligands, which are essential for organometallic catalysts, can be bypassed. Contrary to that, ligands remain almost always required for palladium atoms stabilized on commonly used functionalized carbon and carbon nitride supports, as the catalysts otherwise show limited activity. Despite this, ligand optimization has received little attention, and their role in activating SACs is poorly understood. Here, we explore the impact of structurally diverse phosphine ligands on the performance of nitrogen-doped carbon supported single-atoms (Pd1@NC) in the Sonogashira-Hagihara (SH) cross-coupling reaction, using X-ray absorption spectroscopy and density functional theory simulations to rationalize the observed trends. Compared to the ligand-free SAC, SH activity is enhanced in almost all ligand-assisted systems, with reactivity varying by up to 8 orders of magnitude depending on the ligand choice. Distinct trends emerge based on the free ligand volume and ligand class. Unlike molecular systems, the electronic effects of phosphine ligands are less significant in SACs due to the modulating influence of the support. Instead, the performance of SAC-ligand systems is governed by a balance between the ligand deformation energy during coordination with metal centers, and their resulting accessibility to cross-coupling reagents. These findings offer key insights into optimizing Pd-SACs by leveraging phosphine ligands to activate metal centers and tailor the 3D environment.

An efficient and flexible approach for local distortion: distortion distribution analysis enabled by fragmentation.

Distortion can play crucial roles in influencing structures and properties, as well as enhancing reactivity or selectivity in many chemical and biological systems. The distortion/interaction or activation-strain model is a popular and powerful method for deciphering the origins of activation energies, in which distortion and interaction energies dictate an activation energy. However, decomposition of local distortion energy at the atomic scale remains less clear and straightforward. Knowing such information should deepen our understanding of reaction processes and improve reaction design. Herein, an efficient, general and flexible fragmentation-based approach was proposed to evaluate local distortion energies for various chemical and biological molecules, which can be obtained computationally and/or experimentally. Moreover, our distortion analysis is readily applicable to multiple structures from molecular dynamics (or the minimum energy path) as well as can be evaluated by different computational chemistry methods. Our systematic analysis shows that our approach not only aids computational and experimental chemists in visualizing (relative) distortion distributions within molecules (distortion map) and identifies the key distorted pieces, but also offers deeper understanding and insights into structures, reaction mechanisms and dynamics in various chemical and biological systems. Furthermore, our analysis offers indices of local distortion energy, which can potentially serve as a new descriptor for multi-linear regression (MLR) or machine learning (ML) modelling.

Towards the synthesis of planar beams whose deformation energy depends on the third gradient of displacement

Towards the synthesis of planar beams whose deformation energy depends on the third gradient of displacement

Computational Insights into Hydrogen Atom Transfer Mediators in C-H Activation Catalysis of Nonheme Fe(IV)O Complexes.

This study presents a detailed density functional theory (DFT) investigation into the mechanism and energetics of C-H activations catalyzed by bioinspired Fe(IV)O complexes, particularly in the presence of N-hydroxy mediators. The findings show that these mediators significantly enhance the reactivity of the iron-oxo complex. The study examines three substrates with varying bond dissociation energies─ethylbenzene, cyclohexane, and cyclohexadiene─alongside the [Fe(IV)O(N4Py)]2+ complex. Mediators N-hydroxyphthalimide (NHPI) and N-hydroxyquinolinimide (NHQI) were chosen for their strong oxidative abilities. The results reveal that NO-H bond cleavage in N-hydroxy compounds occurs more readily than C-H bond cleavage in hydrocarbons, as supported by the Marcus cross-relation applied to H-abstraction. This leads to the rapid formation of aminoxyl radicals, which are more reactive than Fe(IV)O species, lowering the activation energy and enhancing the reaction rate. The C-H bond activation aligns with the Bell-Evans-Polanyi principle, correlating the activation energy with the substrate bond dissociation energy. The investigation reveals that the mediator pathway is favored both thermodynamically and kinetically. Additionally, distortion energy provides a compelling explanation for the observed reactivity trends, further highlighting NHQI's superior efficiency compared to NHPI. Additionally, quantum mechanical tunneling plays a significant role, as evidenced by the computed kinetic isotope effect, which matches experimental data.

Free vibration analysis of bidirectional functionally graded double-tapered beam using the p-version of the finite element method

In this paper, we conducted a frequency analysis of bidirectional functionally graded double-tapered beam (BDFG beam) using the p-version of the finite element method, the beam was modeled by the Euler Bernoulli beam theory, the global matrices of the equation of motion are determined by applying the Lagrange equation on the kinetic and deformation energies. The material properties are assumed to vary along the thickness and width directions according the power-law distribution. The numerical results are obtained by a developed Matlab code and compared with Ansys Workbench and Solidworks for a pure metallic tapered cantilever beam and with previous study for a unidirectional functionally graded tapered cantilever beam (UDFG beam), case studies were carried out to analyze the influence of tapering angles, the power law indeces, and boundary conditions on the natural frequencies of the beam; these studies demonstrate the advantage of the proposed bidirectional functionally graded tapered beam over the metallic and unidirectional functionally (UDFG) beams.

On the criterion of strength of single-lap plate joints

On the basis of experimental data on the fracture of an adhesive layer mating two plates along a given section and the known analytical solution corresponding to the calculation scheme, variants of the fracture criterion that take into account hydrostatic pressure and invariant components of elastic energy are considered. One- and two-parameter criteria are investigated, in which the products of volume and shape deformation energy per layer thickness form the critical flow of elastic energy density. It is shown that the loosening of a thin adhesive layer under a two-parameter criterion quasilinear with respect to the volume strain energy most accurately describes the critical state.

Performance Evaluation of Hybrid PSO-BPNN-AdaBoost and PSO-BPNN-XGBoost Models for Rockburst Prediction with Imbalanced Datasets

The rockburst hazard is a primary geological disaster endangering the environment in underground engineering. Due to the complexity of the rockburst mechanism, traditional methods are insufficient to predict the rockburst hazard objectively, especially when dealing with an imbalanced dataset. To address this issue, the hybrid models of PSO-BPNN-AdaBoost and PSO-BPNN-XGBoost were developed to predict rockburst hazards in this study. First, a rockburst dataset with 266 cases was constructed, containing six indicators: the maximum tangential stress, uniaxial compressive strength, uniaxial tensile strength, elastic deformation energy index, tangential stress index, and brittleness coefficient of strength. Then, the original dataset was oversampled using the synthetic minority oversampling technique (SMOTE) for dataset balancing. Subsequently, the PSO-BPNN-AdaBoost and PSO-BPNN-XGBoost models were constructed and evaluated to have the best accuracies of 0.901 and 0.851, respectively. Finally, the developed models were applied to predict the rockburst hazard in the Daxaingling Tunnel, the Cangling Tunnel, and the Zhongnanshan Tunnel shaft. The results indicate that the obtained rockburst hazard levels are consistent with engineering records, and the developed PSO-BPNN-AdaBoost and PSO-BPNN-XGBoost models are reliable for rockburst prediction.

Research on the Mechanical Properties of Elliptical Negative Poisson’s Ratio Structures

A negative Poisson’s ratio structure has special deformation behavior and energy absorption characteristics, and is a new structure with broad application prospects. However, most of the current research is still at the micro theoretical level, and there is less research on the macro mechanical properties. Therefore, this paper proposes a polyurethane elliptical negative Poisson’s ratio structure (PES), uses the methods of experimental simulation and numerical simulation to carry out a mechanical comparison with a concave negative Poisson’s ratio structure (PCS) and analyze the influence of length–width ratio on the structure, highlighting the advantages of the PES in energy absorption, and using parameter analysis to study the influence of the structural form and material properties on the Poisson’s ratio and elastic modulus of the PES, so as to provide a scientific basis and technical support for the application of the structure in high-end equipment manufacturing, seismic isolation and other fields.

Multiscale Concurrent Topology Optimization and Mechanical Property Analysis of Sandwich Structures.

Based on the basic theoretical framework of the Bi-directional Evolutionary Structural Optimization method (BESO) and the Solid Isotropic Material with Penalization method (SIMP), this paper presents a multiscale topology optimization method for concurrently optimizing the sandwich structure at the macro level and the core layer at the micro level. The types of optimizations are divided into macro and micro concurrent topology optimization (MM), macro and micro gradient concurrent topology optimization (MMG), and macro and micro layered gradient concurrent topology optimization (MMLG). In order to compare the multiscale optimization method with the traditional macroscopic optimization method, the sandwich simply supported beam is illustrated as a numerical example to demonstrate the functionalities and superiorities of the proposed method. Moreover, several samples are printed through micro-nano 3D printing technology, and then the static three-point bending experiments and the numerical simulations are carried out. The mechanical properties of the optimized structures in terms of deformation modes, load-bearing capacity, and energy absorption characteristics are compared and analyzed in detail. Finally, the multiscale optimization methods are extended to the design of 2D sandwich cantilever beams and 3D sandwich fully clamped beams.

Impact of solar panel spacing on wind load in an elevated solar panel structure

This study looks at the modeling and stability analysis of an existing elevated solar structure to allow solar energy production and agriculture on the same land (Agrivoltaics). The existing elevated structure accommodates 32 solar panels, each with a capacity of 345 W at a height of approximately 6 m at the center. The impact of the gaps in the 32-panel configuration at this height on the wind load in the elevated solar structure is determined.The study uses computational fluid dynamics (Solid Works Flow simulation) followed by the results used in the static study (Solid Works simulation) to assess the overall stress and strain resulting in the elevated structure. Distortion Energy theory is followed to compare the von Mises stress resulting from the simulation with the Yield strength of the material used to construct the elevated support structure. The findings demonstrate that solar panel spacing can be a key factor in lowering wind loads on the raised support structure.

HLEBI (Homogeneous Low Potential Electron Beam Irradiation) Induced Tensile Elongation of 3D Printed Short Carbon Fiber Reinforced Polyamide (3D-SCFRPA66)

It is a serious problem that short carbon fiber reinforced polyamide 66 (SCFRPA66) cannot be easily shaped by 3D-printing for practical usages. In order to improve on the brittleness, homogeneous low potential electron beam irradiation (HLEBI) to both sides of 3D-SCFRPA66 samples was found to increase strain at tensile strength (εts), corresponding to homogeneous deformation and fracture strain (εf), as well as resistant energy of homogeneous deformation (Ehd), whereas the HLEBI decreased the tensile strength (σts). This improvement in ductility can be explained by lone pair electrons, dangling bond generation, shortening and relaxation of the polymeric chains by the HLEBI.

R3c to P4bm phase transition assisted small to large polaron crossover in sodium bismuth titanate-based ferroelectrics

Sodium bismuth titanate (NBT) reveals a rhombohedral (R3c) phase at room temperature. Ferroelectricity reduces with the advent of a tetragonal (P4bm) phase at the depolarization temperature, Td ∼ 456 K. AC conductivity (σac) studies exposed a small-to-large polaron transition at Td. Barrier energy (WH) was ∼1.60 eV at T < Td for the small polarons in the R3c phase, which drastically reduced to ∼0.043 eV with the advent of the P4bm phase for the large polarons for T > Td. This is associated with the sharp rise in conductivity for T > Td. Ab initio calculations consider the electronic distortion due to oxygen vacancies, which creates trap states in the band structure. The energy gap (ΔE) between the trap states and the conduction band was ∼1.4 eV (R3c) and ∼0.2 eV (P4bm). These values are comparable to the experimental WH. The P4bm phase is more distorted than the R3c phase from charge density and structural distortion calculations. This indicates the formation of large polarons in the P4bm phase, compared to that of small polarons in R3c. The formation energy of the polaron (Epolaron) was calculated from the structural distortion and electron localization energies. The P4bm phase shows lower Epolaron (−0.26 eV) than R3c (−0.36 eV), indicating higher conductivity for the P4bm phase. NBT was chemically modified by adding BCZT to validate the small to large polaronic crossover at Td. This is discussed in light of σac measurements. WH decreased with BCZT incorporation, thereby increasing the conductivity. This is a consequence of the increased lattice distortion due to BCZT incorporation.

Analysis of the Deformation Energy Dissipation in a Layered Medium Under Dynamic Loading (On the Example of Highways)

Analysis of the Deformation Energy Dissipation in a Layered Medium Under Dynamic Loading (On the Example of Highways)

Prediction of multistage fatigue curve based on the relaxation model of irreversible cyclic deformation

The paper studies the multi-stage fatigue dependence (Wöhler diagram) of the material and proposes a new model for its prediction based on considering the mechanisms of plastic deformation and fracture under cyclic loads and a combination of relaxation processes with the evolutionary development of damage, for which the initial condition is formed using the calculation calculated during the cycling process energy of irreversible deformation. The performance of the model is verified using the results of cyclic deformation tests on DP500 steel as an example. It is shown that within the framework of a unified approach it is possible to simultaneously evaluate the short-term, fatigue and long-term strength of the material.

Investigation into the mechanical properties and impact tendency of coal-rock composite structures with peridynamics: A study on predicting the occurrence tendency of dynamic pressure in coal-rock structures.

Due to the difficulty in predicting the occurrence of rockburst in deep mining areas,this paper proposes that the use of Peridynamics to analyze the mechanical characteristics of coal-rock composite structures under loading conditions from the perspective of energy, Determine the impact tendency of coal rock composite structures by combining rock elastic deformation energy index (WET) and rock impact energy index (WCF); Use Lammps software to simulate the loading of composite structural materials and compare and verify with experimental results, to more accurately determine the tendency of rockburst occurrence in different coal-rock composite structures.The results indicate that after the specimen reaches the yield stress, the sample exhibits an "X" shaped failure. The coal body has a significant impact on the overall model's fragmentation, and different combination states and ratios can affect the degree of damage in the coal-rock composite structure. which has important theoretical value for rock mechanics research. The research results can reduce the occurrence of rockburst accidents, the difficulty of mine support, and the cost of mining engineering, as well as improve mine safety levels.

The influence of the adiabatic heating coefficient on the near solidus forming process

The Near Solidus Forming (NSF) process represents a critical method for shaping metallic components under extreme temperature conditions. When metals deform plastically, significant amounts of heat can be generated, which is due to the conversion of plastic deformation energy in the material often known is adiabatic heating. In this study, the influence of the adiabatic heating coefficient (AHC) on temperature distribution and plastic strain during NSF process is investigated. For this purpose, three industrial benchmarks previously fabricated using NSF techniques are selected to serve as representative cases for analysis. To conduct the analysis, sensitivity studies is performed at two key temperatures: 1360 °C and 1370 °C. These temperatures are chosen to capture the range of operating conditions typically encountered in industrial NSF applications. The simulation tool FORGE NXT® is utilized to investigate the potential effect of AHC on equivalent plastic strain (EPS). The range of potential AHC values considered is between 85% and 100%, as determined from a comprehensive literature survey. The study suggests that the AHC has a minimal effect on the deformation behaviour of 42CrMo4 steel at NSF condition for the studied benchmarks. The findings of this study provide the inside to the importance of AHC in the developing of a reliable Digital Twin (DT) for industrial NSF application.

An Adaptive Metal-Organic Framework Discriminates Xylene Isomers by Shape-Responsive Deformation.

The separation of xylene isomers, especially para-xylene, is a crucial but challenging process in the chemical industry due to their similar molecular dimensions. Here, a flexible metal-organic framework, Ni(ina)2, (ina = isonicotinic acid) is employed to effectively discriminate xylene isomers. The adsorbent with adaptive deformation accommodates the shapes of isomer molecules, thereby translating their subtle shape differences into characteristic framework deformation energies. Through a combination of multiple local flexibility behaviors, Ni(ina)2 exhibits guest-specific structural transformations that energetically favor para-xylene over other isomers. Single-crystal X-ray diffraction, in situ powder X-ray diffraction, and theoretical investigations validate this "adaptive fitting" mechanism, where the degree of structural deformation scales with the mismatch between the molecular shape and pore geometry. As a result, Ni(ina)2 achieves exceptional para-xylene selectivity in both liquid and vapor phase separations, maintaining a high para-xylene purity and productivity. This work demonstrates a novel strategy of exploiting framework flexibility to address challenging molecular separations and provides fresh insights into the design of selective adsorbents.

Driving factors for the peculiar bond length dependence and tetragonal distortion of (Ag,Cu)(In,Ga)Se2 and other chalcopyrites

Abstract The chalcopyrite alloy (Ag,Cu)(In,Ga)Se2 is a highly efficient thin film solar cell absorber, reaching record efficiencies above 23%. Recently, a peculiar behavior in the bond length dependence of (Ag,Cu)GaSe2 was experimentally proven. The common cation bond length, namely Ga–Se, decreases with increasing Ag/(Ag + Cu) ratio even though the crystal lattice expands. This is opposite to the behavior observed for Cu(In,Ga)Se2, where all bond lengths increase with increasing lattice size. To better understand this peculiar bond length behavior, element-specific bond lengths of (Ag,Cu)InSe2 and Ag(In,Ga)Se2 alloys are determined using extended x-ray absorption fine structure spectroscopy. They show that the peculiar bond length dependence occurs only for (Ag,Cu) alloys, independent of the species of common cation (In or Ga). The bond lengths are used to determine the anion displacements and to estimate their contribution to the bandgap bowing. Again, both behaviors differ significantly depending on the type of alloyed cation. A valence force field approach, relaxing bond lengths and bond angles, is used to describe the structural distortion energy for a comprehensive set of I–III–VI2 and II–IV–V2 chalcopyrites. The model reveals bond angle distortions as main driving factor for the tetragonal distortion and reproduces the literature values with less than 10% deviation. In contrast, the peculiar bond length dependence is not reproduced, demonstrating that it originates from electronic effects beyond the scope of this structural model. Thus, a fundamental understanding of bond length behavior and tetragonal distortion is achieved for chalcopyrite materials, benefiting their technological applications such as high efficiency thin film photovoltaics.

Recrystallization and spheroidization mechanisms in Ti6246 alloy under thermomechanical treatment

This paper provides a detailed analysis of the dynamic microstructure evolution of Ti-6Al-2Sn-4Zr-6Mo alloy (Ti6246) through a 4-pass hot rolling process. Additionally, it examines the effect of heat treatment on microstructure evolution during the post-annealing of the hot-rolled alloy. During the rolling process, dynamic recrystallization (DRX) predominantly takes place in the α-phase, leading to grain refinement and spheroidization as a consequence of DRX and lamellae spheroidization. Spheroidization of the lamellar structure is more pronounced in the 2-pass rolling process, while the level of DRX is greater in the 4-pass rolling process. The dislocations present within the α lamellae accumulate and entangle at the sub-grain boundary, leading to the formation of a high-angle grain boundary (HAGB). Meanwhile, the β phase infiltrates the grain boundaries of the α phase, leading to the formation of spheroidized equiaxed α grains. Schmid factors associated with the pyramidal slip systems are relatively high, facilitating the activation of slip systems during hot rolling processes. The evolution of the α-phase morphology during heat treatment processes in various rolling passes is primarily driven by static recrystallization (SRX) and grain boundary terminal migration mechanisms. The deformed microstructure volume fraction diminishes and transforms into substructures and recrystallized grains through post-annealing. Post-annealing facilitates the dissipation of stored deformation energy with increasing temperature, leading to a decrease in dislocation density and an enhancement in the extent of recrystallization. Accumulated deformation during rolling and the temperature of the heat treatment both play a role in affecting the static spheroidization process. Greater accumulated deformation and elevated post-annealing temperatures are advantageous for achieving grain spheroidization. The grain boundary splitting process is more pronounced, and the deformation energy is elevated during the 3,4-pass rolling.