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During low‐temperature tempering of wear‐resistant steel, ε‐carbide precipitation can effectively relax residual stress, and its microscopic mechanism is currently unclear. To reveal the stress relaxation mechanism during ε‐carbide precipitation, density functional theory calculations are combined with experiments to explore the ε‐carbide growth behavior and the stress evolution. The results show that ε‐carbide precipitation includes two stages: ε‐precursor formation and ε‐carbide nucleation, and ε‐carbide is in situ nucleated from ε‐precursor matrix. The precipitation‐induced stress relaxation behavior mainly occurs in the early stage of ε‐precursor formation and ε‐carbide nucleation. The early stage of ε‐precursor formation and ε‐carbide precipitation can relax the residual stress to 35.73% and 27.07%, respectively. [ABSTRACT FROM AUTHOR]

Dehydrochlorination of 1,3‐dichloropropanol with alkali is a key step to industrially produce epichlorohydrin. But there are many side reactions involved in the synthesis process. In this work, a complete mechanism and kinetics investigation of the related reaction network was constructed. Density functional theory simulation method was first used to simulate the possible reactions so as to confirm the reaction mechanism and simplify the reaction network. Based on the simulation results, the complex reaction network was simplified into a three‐step consecutive reaction. The kinetic parameters of the three consecutive steps, including the order of the reaction, the pre‐exponential factor, and activation energy, were experimentally determined by conductance and other methods. All the experimental results are basically consistent with the simulation. The obtained kinetics data provide a basis for epichlorohydrin synthesis process optimization. [ABSTRACT FROM AUTHOR]

Ammonium perchlorate (AP) catalytic thermal decomposition by metal oxides is complex and there is still no suitable quantitative evaluation method to characterize intrinsic catalytic activity. Here, a new method to quantitatively evaluate the catalytic capability of metal oxides for AP decomposition has been proposed. We introduce two indicators, intrinsic peak temperature (THTD*) and catalytic density (ρT*) in high‐temperature decomposition process, to uncouple activity and number of catalyst sites. Hematite (α‐Fe2O3) nanostructures with different shapes have been used as model catalysts to verify the feasibility of this method. Rod‐like α‐Fe2O3 shows the best catalytic performance in AP decomposition with the lowest THTD* of 345.1°C and highest ρT* of 0.544, which indicate the largest number and highest activity of catalytic sites. Moreover, these new indicators are theoretically proven to be reasonable by density functional theory calculations. [ABSTRACT FROM AUTHOR]

A transition‐metal‐free C(sp2)−C(sp2) bond formation reaction by the cross‐coupling of diazo quinones with catechol boronic esters was developed. With this protocol, a variety of biaryls and alkenyl phenols were obtained in good to high yields under mild conditions. The reaction tolerates various functionalities and is applicable to the derivatization of pharmaceuticals and natural products. The synthetic utility of the method was demonstrated by the short synthesis of multi‐substituted triphenylenes and three bioactive natural products, honokiol, moracin M, and stemofuran A. Mechanistic studies and density functional theory (DFT) calculations revealed that the reaction involves attack of the boronic ester by a singlet quinone carbene followed by a 1,2‐rearrangement through a stepwise mechanism. [ABSTRACT FROM AUTHOR]

Supramolecular ensembles adopting ring‐in‐ring structures are less developed compared with catenanes featuring interlocked rings. While catenanes with inter‐ring closed‐shell metallophilic interactions, such as d10–d10 AuI–AuI interactions, have been well‐documented, the ring‐in‐ring complexes featuring such metallophilic interactions remain underdeveloped. Herein is described an unprecedented ring‐in‐ring structure of a AuI‐thiolate Au12 cluster formed by recrystallization of a AuI‐thiolate Au10 [2]catenane from alkane solvents such as hexane, with use of a bulky dibutylfluorene‐2‐thiolate ligand. The ring‐in‐ring AuI‐thiolate Au12 cluster features inter‐ring AuI–AuI interactions and underwent cluster core change to form the thermodynamically more stable Au10 [2]catenane structure upon dissolving in, or recrystallization from, other solvents such as CH2Cl2, CHCl3, and CH2Cl2/MeCN. The cluster‐to‐cluster transformation process was monitored by 1H NMR and ESI‐MS measurements. Density functional theory (DFT) calculations were performed to provide insight into the mechanism of the "ring‐in‐ring⇌ [2]catenane" interconversions. [ABSTRACT FROM AUTHOR]

A six‐membered ring lactam derivative was introduced in a parallel manner into uranyl–salophens with R/S configuration (R‐/S‐AUSRLs), which were used as receptors to coordinate with guests of cis−/trans‐methylcyclohexylamines (cis−/trans‐MCHAs). Using density functional theory calculations at the B3LYP/6‐311G** level and RECP, an insight into the coordination complexes of the R‐/S‐AUSRLs with cis−/trans‐MCHAs was obtained. The results showed that the U atoms of receptors could coordinate with the N atoms of four kinds of cis−/trans‐1,2 or − 1,4 guests, but the two kinds of cis−/trans‐1,3 guests could not be converged by the same method in the process of structural optimization due to steric hindrance, and thus the cis−/trans‐1,3 guests could not be coordinated with the R‐/S‐AUSRLs. The mode of coordination of the R‐/S‐AUSRLs with the guests displayed a significant difference. And the change of R‐AUSRL coordination ability to the cis−/trans‐MCHAs was very large, but that of S‐AUSRL was small. Overall, the stability of the R‐series coordination complexes was higher than that of the corresponding S‐series coordination complexes, and the R‐AUSRL receptor had better coordination selectivity and higher molecular recognition to the cis−/trans‐MCHA guests than the S‐AUSRL receptor. However, the coordination ability of S‐AUSRL with the cis−/trans‐MCHAs was stronger than that of R‐AUSRL. It was expected that these results could provide insightful information and theoretical guidance for understanding the molecular recognition of R‐/S‐AUSRLs for cis−/trans‐type cyclohexylamine derivatives. [ABSTRACT FROM AUTHOR]

Electronic transport properties in an Al cluster are investigated theoretically in this paper. We propose a possible illustration of Coulomb blockade based on variable electrostatic potential ( ESP). Density functional theory ( DFT) was used to achieve the global minimum structure and wave function for analyzing the ESP and density of states ( DOS) of Al68 in different charged states. Al68 is able to contain multiple electrons. According to the calculation of systematic energy and surface ESP, respectively, the surface of Al68 presents a 0-6.33 eV ESP barrier after electron injection, which is 0 eV at first. The probability density of flow of electrons was calculated under one-dimensional model with double barriers. Expected results were obtained, containing a nonlinear relationship between J and V and flow density steps. Moreover, an assumption is proposed associated with nonlinear conductance phenomenon of zero-dimensional nanomaterials. Significantly, Al films with different thicknesses were prepared by the low vacuum physical vapor deposition ( LVPVD) method, exhibiting novel fluorescent behaviors. In addition, the I-V curve of a 25-nm Al film exhibited two steps at 7 and 27 V, respectively, which meant that the step effect was caused by Coulomb blockade, in accordance with the theoretical calculation. [ABSTRACT FROM AUTHOR]

• 112TCE and NaOH reaction kinetics was studied by simulation and experiment. • The conductometry and substrate concentration amplification method were first used. • The kinetic parameters of three parallel reactions were decoupled. • Kinetic parameters of overall and parallel reactions were obtained. Dehydrochlorination of 1,1,2-trichloroethane (112TCE) is a widely used method for preparing vinylidene chloride (VDC), which is an important polymeric monomer and intermediate of refrigerant. However, there are few reports on kinetics of this reaction system. In this work, density functional theory (DFT) calculation analyses and experiments were conducted to investigate the reaction mechanism and kinetics of 112TCE dehydrochlorination with sodium hydroxide (NaOH). DFT simulation results unveiled there were three parallel reactions which produce VDC, cis -1,2-dichloroethylene (C12DE) and trans -1,2-dichloroethylene (T12DE) respectively in the reaction process of 112TCE and NaOH. The activation energy of the reaction to produce VDC was lower than those of the other two reactions. Moreover, the kinetic parameters of the three parallel reactions, such as reaction orders, rate constants, pre-exponential factors and activation energies, were experimentally obtained by decoupling the overall reaction kinetics. All the parallel reactions are bimolecular elimination reactions and the rate expression of the intrinsic kinetics for generating VDC is d C t dt = 1.668 × 10 11 e - 75662 RT C A C B. The reaction rate is three orders of magnitude higher than those of producing C12DE and T12DE, which is consistent with the DFT simulation results. These kinetics results are useful for the process optimization and reactor design in VDC production process. [ABSTRACT FROM AUTHOR]

Solar CO2 reduction into hydrocarbons helps to solve the global warming and energy crisis. However, conventional semiconductors usually suffer from low photoactivity and poor photostability. Here, atomically-thin oxide-based semiconductors are proposed as excellent platforms to overcome this drawback. As a prototype, single-unit-cell Bi2WO6 layers are first synthesized by virtue of a lamellar Bi-oleate intermediate. The single-unit-cell thickness allows 3-times larger CO2 adsorption capacity and higher photoabsorption than bulk Bi2WO6. Also, the increased conductivity, verified by density functional theory calculations and temperature-dependent resistivities, favors fast carrier transport. The carrier lifetime increased from 14.7 to 83.2 ns, revealed by time-resolved fluorescence spectroscopy, which accounts for the improved electron-hole separation efficacy. As a result, the single-unit-cell Bi2WO6 layers achieve a methanol formation rate of 75 µmol g-1 h-1, 125-times higher than that of bulk Bi2WO6. The catalytic activity of the single-unit-cell layers proceeds without deactivation even after 2 days. This work will shed light on designing efficient and robust photoreduction CO2 catalysts. [ABSTRACT FROM AUTHOR]

The bottleneck in water electrolysis lies in the kinetically sluggish oxygen evolution reaction (OER). Herein, conceptually new metallic non-metal atomic layers are proposed to overcome this drawback. Metallic single-unit-cell CoSe2 sheets with an orthorhombic phase are synthesized by thermally exfoliating a lamellar CoSe2-DETA hybrid. The metallic character of orthorhombic CoSe2 atomic layers, verified by DFT calculations and temperature-dependent resistivities, allows fast oxygen evolution kinetics with a lowered overpotential of 0.27 V. The single-unit-cell thickness means 66.7 % of the Co2+ ions are exposed on the surface and serve as the catalytically active sites. The lowered Co2+ coordination number down to 1.3 and 2.6, gives a lower Tafel slope of 64 mV dec−1 and higher turnover frequency of 745 h−1. Thus, the single-unit-cell CoSe2 sheets have around 2 and 4.5 times higher catalytic activity compared with the lamellar CoSe2-DETA hybrid and bulk CoSe2. [ABSTRACT FROM AUTHOR]

A model of doping confined in atomic layers is proposed for atomic-level insights into the effect of doping on photocatalysis. Co doping confined in three atomic layers of In2S3 was implemented with a lamellar hybrid intermediate strategy. Density functional calculations reveal that the introduction of Co ions brings about several new energy levels and increased density of states at the conduction band minimum, leading to sharply increased visible-light absorption and three times higher carrier concentration. Ultrafast transient absorption spectroscopy reveals that the electron transfer time of about 1.6 ps from the valence band to newly formed localized states is due to Co doping. The 25-fold increase in average recovery lifetime is believed to be responsible for the increased of electron-hole separation. The synthesized Co-doped In2S3 (three atomic layers) yield a photocurrent of 1.17 mA cm−2 at 1.5 V vs. RHE, nearly 10 and 17 times higher than that of the perfect In2S3 (three atomic layers) and the bulk counterpart, respectively. [ABSTRACT FROM AUTHOR]

A morpholine-functionalized pyrrole-cyanine probe was synthesized via a simple condensation reaction in high yield. This probe exhibits high selectivity toward ClO− on fluorescence and UV–vis spectra in neat aqueous solution. The strong green emission of the probe solution was quenched and the yellow color faded immediately upon the addition of ClO−. The detection limit of the probe for ClO− was 0.165 μM. The mechanism of hypochlorite-induced C C breakage was supposed on the basis of EIS-MS, NMR, and density functional theory (DFT) calculation. Finally, the probe was utilized to image ClO− in lysosomes of living cells. Unlabelled Image • A morpholine functionalized pyrrole-cyanine probe has been developed. • The probe could detect ClO− in 100% aqueous solution on both fluorescence and UV–vis spectra. • The probe has been applied for imaging lysosomal ClO− in living cells. [ABSTRACT FROM AUTHOR]

Abstract In future fusion devices, the incident hydrogen plasma with high mobility can diffuse deep into tungsten bulk, which is directly relevant with hydrogen isotopes permeation and retention in tungsten. In this work, density functional theory (DFT) and object kinetic Monte Carlo (OKMC) simulations are adopted to investigate the hydrogen diffusion behavior in tungsten under anisotropic uniaxial strain from −2.5% to 2.5%. As presented by our DFT calculations, there are two types of hydrogen diffusion paths when applying strain, including one path perpendicular to the strain direction and another path largely along the strain direction. The migration energy barriers of these two paths have opposite variation tendencies in tensile or compressive condition. Our OKMC calculations based on DFT input show that, in tensile condition, the hydrogen diffusion is restrained despite the lower energy barrier of the corresponding diffusion path. In compressive condition, the hydrogen diffusion along the strain direction is enhanced, while that perpendicular to the strain direction is suppressed. The hydrogen diffusivity under anisotropic strain at the temperature range from 400 K to 1800 K is determined. It is demonstrated that tensile strain can suppress the diffusivity, while compressive strain can either suppress or facilitate the diffusivity depending on the temperature and the strain value. The anisotropic strain exhibits distinct effect on hydrogen diffusivity at lower temperature but its effect is minimal as the temperature increases. Highlights • In anisotropic tensile strained tungsten, the hydrogen inclines to diffuse perpendicular to the strain direction. • In anisotropic compressive strained tungsten, the hydrogen tends to diffuse largely along the strain direction. • The anisotropic tensile strain can suppress the hydrogen diffusivity in tungsten. • The effect of anisotropic strain on the hydrogen diffusivity in tungsten decreases as temperature increases. [ABSTRACT FROM AUTHOR]

The cellulose, which is one of the most abundant solid by-products of agriculture and forestry industry, has been successfully tested for the synthesis of nitrogen and phosphorus co-doped carbon-based metal-free catalysts (NPC) via freeze-drying the mixture of cellulose crystallite and ammonium phosphate, followed by annealing of the hydrogel under nitrogen atmosphere at 800 °C for 2 h. Different techniques including TEM, SEM, FTIR and XPS spectroscopy have been applied to characterize the as-prepared NPC, which presents flake-like morphology with N and P doping levels of 4.3 atom% and 10.66 atom%, respectively. The NPC exhibits excellent catalytic activity for the reduction of p -nitrophenol (p -NP). The turnover frequency (TOF) of the reduction of p- NP is as high as 2 × 10−5 mmol·mg−1·min−1 and the apparent kinetic rate constant was calculated as 0.0394 min−1 at room temperature. The catalytic mechanism is proposed by combining the density functional theory calculation and analysis of the experimental results. These findings open up new possibilities of valorization for cellulose-based by-product and treatment of p -NP-based wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • This study used sesquiterpenoids with 97 carbon skeletons for model construction. • The scheme based on the DFT method combined with triple correction can accurately calculate Δ c H of sesquiterpenoid HEDFs. • We developed the MLR equation with only 4 features for predicting Δ c H for sesquiterpenoid HEDFs. • The proposed DFT-QSPR scheme can effectively guide the design of novel sesquiterpenoid HDEFs. Sesquiterpenoids that are renewable and have high energy density and low freezing point are promising biomass high-energy–density fuels (HEDFs). The enthalpy of combustion (Δ c H) is the key characteristic to measure the heat energy content of HEDFs. Its accurate theoretical prediction and evaluation is essential for designing novel sesquiterpenoid HEDFs. Combining the screened and optimized density functional theory (DFT) method with triple computational correction, we presented a standardized calculation scheme for Δ c H with an average absolute error of only 2.6 % by 295 structurally diverse sesquiterpenoid HEDFs. Then, the extreme gradient boosting (XGBoost) algorithm was used to determine the correlation between the calculated Δ c H and 54 quantum chemical (QC) descriptors and the shapley additive explanation (SHAP) method to elucidate the key factors affecting Δ c H. Lastly, a quantitative structure–property relationship (QSPR) prediction model with only four QC features was constructed by using the SHAP results via the multiple linear regression (MLR) algorithms. Notably, the model has excellent prediction performance, decreased complexity, and improved applicability. The coefficient of determination (R 2) of the internal training set and external test set of the model are 0.957 and 0.956, while the root mean square error (RMSE) are 8.626 kcal/mol and 9.012 kcal/mol, respectively. The proposed DFT-QSPR (the ingenious combination of DFT and QSPR) scheme can effectively guide the design of Δ c H of novel sesquiterpenoid HDEFs. [ABSTRACT FROM AUTHOR]

Typically, silica-alumina zeolites are hydrothermally synthesized in the sodium-rich dense hydrogel systems with a relatively long crystallization time in industry. The fast and economical synthesis of silica-alumina zeolites is still a big challenge. Herein, we develop a universal method to tackle this issue using the rotating packed bed (RPB). An interesting phenomenon is found that gel-liquid interfacial areas in the zeolite precursor are obviously enlarged when RPB is employed, and thus the following crystallization rates of zeolites are greatly improved, especially for the initial nucleation process. Also, we successfully control the growth rates of silica-alumina zeolite by adjusting the gel-liquid interfacial areas. Furthermore, we find that the transfer rate of OH− and hydrated sodium ions from liquid part to gel phase is enhanced by RPB in the initial nucleation process, which greatly promotes the nucleation rate of zeolites. The density functional theory (DFT) calculations demonstrate that hydrated sodium ions can induce the dehydrogenation of Si–OH to generate reactive oxygen radicals, thus lowering the energy barrier of the polymerization reaction and consequently accelerating the nucleation process. Moreover, NaY, NaZSM-5, and NaA zeolites with larger surface areas and more pore volumes are successfully synthesized by this RPB-enhanced-interface strategy, and their crystallization processes are all greatly accelerated. The gel-liquid interfacial areas in the zeolite precursor are obviously enlarged when RPB is employed, which reduces the diffusion resistance of sodium ions from liquid to gel phase in the early period of zeolite nucleation. DFT calculations indicate that sodium ions can induce the dehydrogenation of Si–OH to generate the oxygen free radical, which lowers the energy barrier of zeolite nucleation. Thus, RPB-enhanced-interface strategy can effectively accelerate the nucleation and crystallization process of zeolite. [Display omitted] • Rotating packed bed (RPB) can effectively accelerate the growth process of zeolites. • Zeolites prepared with RPB exhibit relatively large surface areas and pore volumes. • The diffusion resistance of active species in the zeolite synthetic system can be reduced. • Sodium ions promote zeolite nucleation via inducing the generation of oxygen radical. [ABSTRACT FROM AUTHOR]

• Sub-10 nm Co 3 O 4 is synthesized by surfactant-free precipitation in RPB reactor. • The size of Co 3 O 4 nanoparticle is inherited from the thickness of precursory Co(OH) 2. • Sub-10 nm Co 3 O 4 shows the best catalytic performance for AP decomposition. • Size effect of Co 3 O 4 in AP decomposition has been studied experimentally and theoretically. Sub-10 nm Co 3 O 4 nanoparticles with a narrow size distribution are prepared by a surfactant-free liquid precipitation method in a rotating packed bed (RPB) reactor. The mean size of the material is about 8.5 nm, and is the smallest among previous reports via surfactant-free liquid precipitation. The growth mechanisms show that the sizes of Co 3 O 4 nanoparticles inherit from the precursory Co(OH) 2. Compared to the traditional stirred tank reactor, RPB can enhance the nucleation of Co(OH) 2 through enhanced micro-mixing, which leads to thinner and more uniform products. As-prepared Co 3 O 4 can show enhanced catalytic performance for ammonium perchlorate (AP) decomposition. The peak temperatures of AP decomposition reduce to 296.8 °C, 291.8 °C, 290.0 °C, and 286.6 °C by adding 2 wt% 22.6 nm, 15.0 nm, 10.9 nm, and 8.5 nm of Co 3 O 4 nanoparticles, respectively. Density functional theory (DFT) calculations and thermogravimetry coupled with mass spectrometry (TG-MS) analysis reveal that the size-dependent catalytic activity of Co 3 O 4 for AP decomposition origin from varied O 2 activation ability and NH 3 adsorption capacity at the edge and corner sites. [ABSTRACT FROM AUTHOR]

[Display omitted] • Yolk-shell B/N-HCNS@V O -G enables a selective and durable two-electron oxygen reduction reaction process. • High-yield electrosynthesis of H 2 O 2 is realized by our dual-defective B/N-HCNS@V O -G. • Electro-synthetic H 2 O 2 with oxidizing ability allow the on-site degradation of organic pollutants. • V O -G armor is proven to enhance both catalytic activity and durability of B/N-HCNS. Electrocatalytic 2e− oxygen reduction reaction (ORR) strategy for decentralized and on-demand production of H 2 O 2 has emerges as an appealing alternative to prevailing anthraquinone process. Nevertheless, the sustainable development of high-performance and low-cost electrocatalysts with high selectivity and durability remains elusive. Herein, we report a metal-free electrocatalyst affording B/N co-doped yolk-shell carbon nanosphere with oxygen-vacancy-decorated graphene armor (B/N-HCNS@V O -G) toward promoted 2e− ORR in alkaline media. Such a dual-defective electrocatalyst harvests excellent H 2 O 2 electrosynthesis performance with a high selectivity of 91 % and a stable operation of 24 h, which is markedly superior to its counterparts and compares favorably with the state-of-the-arts. Density functional theory calculations further reveal the essential roles of defective graphene coating played in advancing the 2e− ORR selectivity of B/N-HCNS@V O -G. More impressively, thus-produced H 2 O 2 (realizing a high yield of 56 ppm at 0.7 V) satisfies an in-situ antibiotic and dye degradation, holding practical promise for on-site wastewater remediation. [ABSTRACT FROM AUTHOR]