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This study explores the enhancement of aqueous zinc-ion batteries (AZIBs) using ammonium-enhanced vanadium oxide cathodes. Density Functional Theory (DFT) calculations reveal that NH4+ incorporation into V6O16 lattices significantly facilitates Zn2+ ion diffusion by reducing electrostatic interactions, acting as a structural lubricant. Subsequent experimental validation using (NH4)2V6O16 cathodes synthesized via a hydrothermal method corroborates the DFT findings, demonstrating remarkable electrochemical stability with a capacity retention of 90% after 2000 cycles at 5 A g−1. These results underscore the potential of NH4+ in improving the performance and longevity of AZIBs, providing a pathway for sustainable energy storage solutions. [ABSTRACT FROM AUTHOR]

Using density functional theory (DFT), the density of states of NH4V3O8 (NVO) was analyzed pre- and post-oxygen defect (Od) formation. The findings revealed a reduced bandgap in NVO after Od introduction, emphasizing the role of Od in enhancing conductivity of the material, thus improving its electrochemical attributes. Through the water bath method, both NVO and its oxygen-deficient counterpart, (NH4)2V10O25·8H2O (NVOd), were synthesized as potential cathode materials for aqueous zinc-ion batteries (AZIBs). Experimental outcomes resonated with DFT predictions, highlighting the beneficial role of oxygen defects in boosting electrical conductivity. Notably, the refined material displayed a remarkable capacity of 479.3 mAh g−1 at 0.1 A g−1, underscoring its promise for advanced energy storage solutions. [ABSTRACT FROM AUTHOR]

The structure of aq. sodium acetate solution (CH3COONa, NaOAc) was studied by X-ray scattering and density function theory (DFT). For the first hydrated layer of Na+, coordination number (CN) between Na+ and O(W, I) decreases from 5.02 ± 0.85 at 0.976 mol/L to 3.62 ± 1.21 at 4.453 mol/L. The hydration of carbonyl oxygen (OC) and hydroxyl oxygen (OOC) of CH3COO− were investigated separately and the OC shows a stronger hydration bonds comparing with OOC. With concentrations increasing, the hydration shell structures of CH3COO− are not affected by the presence of large number of ions, each CH3COO− group binds about 6.23 ± 2.01 to 7.35 ± 1.73 water molecules, which indicates a relatively strong interaction between CH3COO− and water molecules. The larger uncertainty of the CN of Na+ and OC(OOC) reflects the relative looseness of Na-OC and Na-OOC ion pairs in aq. NaOAc solutions, even at the highest concentration (4.453 mol/L), suggesting the lack of contact ion pair (CIP) formation. In aq. NaOAc solutions, the so called "structure breaking" property of Na+ and CH3COO− become effective only for the second hydration sphere of bulk water. The DFT calculations of CH3COONa (H2O)n=5–7 clusters suggest that the solvent-shared ion pair (SIP) structures appear at n = 6 and become dominant at n = 7, which is well consistent with the result from X-ray scattering. [ABSTRACT FROM AUTHOR]

The development of novel high energy density materials (HEDMs) with balanced detonation performance and sensitivity is a long-term goal in the energetic material field. In this work, by means of density functional theory, we systematically investigated physicochemical and energetic properties of three novel HEDMs constructed from furazan and piperazine frameworks with zero oxygen balance. Our results show that all these compounds have high densities (2.01–2.06 g·cm −3 ), positive heats of formation (94.48–1132.95 kJ·mol −1 ), excellent detonation performance (detonation velocity 9.24–9.85 km·s −1 ; detonation pressure 40.33–46.47 GPa) and acceptable impact sensitivity ( H 50 26–44 cm). However, based on bond dissociation energy (BDE) calculations, it is found that only compound 1 is thermally stable. Given these properties, it could be expected compound 1 is the most promising HEDM with acceptable sensitivity. Meanwhile, in this work, it is also demonstrated that the introduction of coupled heterocyclic backbone and zero oxygen balance is an effective strategy to achieve a good balance between detonation performance and sensitivity. [ABSTRACT FROM AUTHOR]

An investigation on the structural, electronic, thermodynamic, and mechanical properties of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)/2-methylpyridine-N-oxide (MPNO) cocrystal was carried out from 0 to 100 GPa by using a dispersion-corrected density functional theory (DFT-D) method. Our calculated crystal structure is in excellent agreement with experimental results at ambient pressure. Based on the analysis of lattice parameters, lattice angles, bond lengths, bond angles, and dihedral angles under high pressure, we observe that HMX molecules in the cocrystal bulk are seriously distorted but MPNO molecules remain relatively unchanged. Hydrogen bond lengths are greatly shortened under high pressure. In addition, with the increase in pressure, the bandgap decreases gradually. However, it increases suddenly at 70 GPa. Some important hydrogen bonds between HMX and MPNO are also observed in the density of states spectrum. According to the thermodynamic analysis, this cocrystal is more easily prepared under low pressure. Finally, we characterized its mechanical properties and the results show that this cocrystal is malleable in nature. We expect that this research can provide a fundamental basis for further HMX cocrystal design and preparation. [ABSTRACT FROM PUBLISHER]

A novel 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX)/pyridine-N-oxide (PNO) cocrystal at 1:1 molar ratio was synthesized by a solvent evaporation method, and its crystal structure was determined using X-ray diffraction (XRD). It crystallizes in the orthorhombic system with thePbcn space group and cell parametersa = 12.712(3)Å,b = 9.315(3)Å,c = 12.909(3)Å. In addition, detonation performance of this cocrystal was estimated. The predicted detonation velocity and detonation pressure of this cocrystal are 7.47 km/s and 23.20 GPa, respectively, suggesting that it is less powerful than β-HMX. Finally, density functional theory, involving binding energy, atoms in molecule (AIM) theory, natural bond orbital (NBO) analysis, band structure, and density of states, was adopted to characterize the driving forces for the formation of this cocrystal. The results show that driving forces are dominated by the interactions between O atoms of PNO and methylene groups of HMX. It is expected that this research provides some bases for further HMX cocrystal design and preparation. [ABSTRACT FROM PUBLISHER]

The free H atom existing in flame plays vital role in combustion chemistry. As a continuation of our previous study, the possibility of forming the first aromatic ring via the self-recombination reaction of but-1-ene-3-yne (C 4 H 4 ) with H-assistance was investigated in the present study. The potential energy surfaces were calculated with density functional theory and indicate that the C 4 H 4 + C 4 H 4 (+H) reaction can generate 6-membered ring, ring-opening and 5-membered ring structures. The zero point energies of the investigated molecules were obtained at CBS-QB3 level, and the reliability of energy calculation was checked with T1 diagnostic. The rate coefficients were calculated using conventional transition state theory (TST) and Rice-Ramsperger-Kassel-Marcus (RRKM) theory with solving master equation. By comparing the rate coefficients and branching ratio of product, we found that the CS10 + H, CS16, CS19 and CS38 are the dominant product of C 4 H 4 + C 4 H 4 (+H) reaction in the temperature range of 500–2500 K, and the formation of other products can be ignored. The self-dehydrogenation reaction is the essential step in the formation of the main product CS10 + H. Similar to H-transfer reactions, the self-dehydrogenation reactions are found to be sensitive to the molecular structure in terms of the energy barrier. [ABSTRACT FROM AUTHOR]

Detailed mechanisms of C 4 H 4 + C 4 H 4 reaction were investigated by accurate ab initio density functional theory B3LYP/6-311 + G(d,p) calculations, as well as CBS-QB3 calculations. It was found that styrene, phenylacetylene and 5-membered ring structure can be formed in C 4 H 4 + C 4 H 4 reaction through five parallel and competing pathways. Three pathways are featured with H-transfer and dehydrogenation reactions, and the other two pathways are characterized with the forming and breaking of C–C bond. The H-transfer reactions play a vital role in stabilizing intermediates. It was found that the H-transfer reaction is significantly dependent on the relative position of two C atoms, the degree of saturation of the second C atom, and the electronic environment of molecule. Generally, an ortho-position unsaturated C atom with relative small positive atomic charge is preferable in H-transfer reaction. The yield of products and reaction rate coefficients were evaluated by using Rice−Ramsperger−Kassel−Marcus theory with solving master equation at different combustion temperatures and pressures ( T = 800–2500 K, P = 0.1–10 atm). The kinetic results indicate that styrene is the dominant product and the formation of other two products can be ignored when temperature is lower than 1600 K. The formations of phenylacetylene and 5-membered ring structure are only facilitated at higher temperature, but dependent on the combustion pressure. Specifically, phenylacetylene is favored by higher pressure and higher temperature, while 5-membered ring structure is favored by lower pressure and higher temperature. [ABSTRACT FROM AUTHOR]

Detailedmechanisms of PAH growth involving methylene (CH2) werestudied using accurate ab initio density functional theory B3LYP/6-311+G(d,p)calculations, as well as approximate QCISD(T,full)/6-311++G(3df,2pd)calculations. The PAH growth can be divided into five essential reactionsteps, namely, addition C2H2→ intramolecularhydrogen migration → addition CH2→ cyclization→ H-elimination. The aliphatic species of indene and 1H-phenaleneare found in the pathways of PAH growth, which is in accord with theexperimental results that reveal the formation of aliphatic speciesin flames. It was found that the simultaneous removal of two H atomsin one reaction step is feasible in PAH evolution, and this can reasonablyinterpret the absence of a H atom in the post-flame region. The correspondingrate coefficients at 1 atm were evaluated by using TST and RRKM theoryby solving the master equations in the temperature range of 500–2500K. The calculated branching ratios suggest that the pathways involvingCH2are competitive in PAH growth. [ABSTRACT FROM AUTHOR]

Thermaldecompositions of polycyclic aromatic hydrocarbon (PAH)oxyradicals on various surface sites including five-membered ring,free-edge, zigzag, and armchair have been systematically investigatedby using ab initio density functional theory B3LYP/6-311+G(d,p) basisset. The calculation based on Hückel theory indicates thatPAHs (3H-cydopenta[a]anthracene oxyradical) withoxyradicals on a five-membered ring site have high chemical reactivity.The rate coefficients of PAH oxyradical decomposition were evaluatedby using Rice–Ramsperger–Kassel–Marcus theoryand solving the master equations in the temperature range of 1500–2500K and the pressure range of 0.1–10 atm. The kinetic calculationsrevealed that the rate coefficients of PAH oxyradical decompositionare temperature-, pressure-, and surface site-dependent, and the oxyradicalon a five-membered ring is easier to decompose than that on a six-memberedring. Four-membered rings were found in decomposition of the five-memberedring, and a new reaction channel of PAH evolution involving four-memberedrings is recommended. [ABSTRACT FROM AUTHOR]

In this work, properties of polynitro-bridged pyridine derivatives were systemically studied at the B3LYP/6-31G(d) level. Gas-phase heats of formation (HOFs) for the designed compounds were calculated using isodesmic reactions, and their solid-phase HOFs were estimated using the Politzer approach. All designed compounds possess large solid-phase HOFs, larger than 700 kJ/mol. Based on the predicted crystal densities, solid-phase HOFs, and chemical energies, detonation properties were evaluated by means of Kamlet-Jacobs empirical equations. The results show that detonation velocities and pressures of all of the designed compounds are above 9.30 km/s and 40.00 GPa, respectively. In addition, bond dissociation energy (BDE) was employed to investigate their thermal stability. Considering solid-phase HOFs, detonation performance, and thermal stability, most of the designed compounds meet the requirements of high energy density materials (HEDMs). [ABSTRACT FROM PUBLISHER]

interactions and properties of octahydro-1,3,5,7-tetranitro-1,3,5,7- tetrazocine (HMX) / 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) cocrystal were studied by using the dispersion-corrected density functionals (ωB97XD, B97D) and meta-hybrid functional (M062x) methods. Binding energies, heats of formation, thermodynamic properties, atoms in molecules, and natural bond orbital analysis were performed to investigate HMX/LLM-105 complexes. Results show that the main interactions between HMX and LLM-105 are CH...O, NH...O, N...O, and O...O interactions. In addition, Monte Carlo simulation was employed to predict the crystal structure of HMX/LLM-105 cocrystal. The HMX/LLM-105 cocrystal is most likely to crystallize in C2/c space group, and its corresponding cell parameters are Z = 8, a = 41.63 Å, b = 6.77 Å, c = 45.63 Å, ß = 164.55°, and ρ = 1.99 g/cm3. Detonation velocity and pressure of HMX/LLM-105 cocrystal are 8.95 km/s, 37.69GPa, a little lower than those of HMX (9.10 km/s, 37.76GPa). However, according to the net charges of nitro group, HMX/LLM-105 cocrystal exhibits less sensitive than HMX. Finally, bond dissociation energy calculation shows that HMX/LLM-105 complexes are thermally stable. Considering , sensitivity, and detonation performance, HMX/LLM-105 cocrystal meets the requirements of insensitive high energy density materials. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Highlights: [•] HMX/DMI cocrystal explosive was synthesized and characterized by using X-ray single crystal diffraction. [•] Binding energies, atoms in molecules (AIM), natural bond orbital (NBO), band structure and density of states were employed to investigate host–guest interactions. [•] Results show that the main driving forces is hydrogen bondings between methylene group of HMX and O atoms of DMI. [ABSTRACT FROM AUTHOR]

Gas-phase heats of formation (HOF), solid-phase HOF, detonation properties, electronic structure and thermal stability for a series of polynitro pyrazine derivatives containing three heterocycles have been investigated using density functional theory. It is found that the nitro group is an efficient tool to improve HOF of pyrazine derivatives. Furthermore, detonation velocities and detonation pressures of these compounds are evaluated using empirical Kamlet-Jacobs equations. As a result, it indicates that the nitro group is useful to enhance detonation properties. Detonation velocities of five compounds are 9.67, 9.20, 9.74, 9.76 and 9.87 km/s, respectively, which are significantly larger than that of HMX (9.10 km/s). Bond dissociation energy is also performed to investigate their thermal stability, showing that thermal stability of these compounds is little affected by nitro groups or the position of substituent groups. Considering solid-phase HOF, detonation properties and thermal stability, some of pyrazine derivatives can be potential high energy density materials. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Highlights: [•] The pyrazine based compounds designed to estimate structure–performance relationship. [•] Pyrazine derivatives exhibit better detonation performance. [•] Bond dissociation energies of weakest N–NO2 bonds calculated to predict thermal stability. [ABSTRACT FROM AUTHOR]

Abstract: The molecular structures and intramolecular proton transfer reaction of 1-phenyl-3-methyl-4-(6-hydro-4-amino-5-sulfo-2,3-pyrazine)-pyrazole-5-one have been investigated with both ab initio method and the density functional theory. The solvent effects are simulated using the self-consistent reaction field (SCRF) method within the framework of the polarizable continuum model (PCM). The results show that the computed geometrical parameters at the B3LYP levels are in better agreement with experimental values than those at the RHF levels, and the choice of functional in DFT plays an important role in describing the title compound. It is found that strong hydrogen bonds (O–H···N and O···H–N) exist in the title compound, and in the proton transfer process, the O–H bond is broken while the N–H bond is formed. In addition, the order of stability of the isomers remains the same in different solvents, while the barrier height of the proton transfer reaction and dipole moments for the title compound grow with the increase of the solvent polarity. Eventually, the NBO analysis shows that the strength of the hydrogen bond reduces with the increase of the solvent polarity. [Copyright &y& Elsevier]

Currently, in addition to the electroactive non‐noble metal water‐splitting electrocatalysts, a scalable synthetic route and simple activity enhancement strategy is also urgently needed. In particular, the well‐controlled synthesis of the well‐recognized metal–metal nanointer face in a single step remains a key challenge. Here, the synthesis of Cu‐supported Ni4Mo nanodots on MoOx nanosheets (Ni4Mo/MoOx) with controllable Ni4Mo particle size and d‐band structure is reported via a facile one‐step electrodeposition process. Density functional theory (DFT) calculations reveal that the active open‐shell effect from Ni‐3d‐band optimizes the electronic configuration. The Cu‐substrate enables the surface Ni–Mo alloy dots to be more electron‐rich, forming a local connected electron‐rich network, which boosts the charge transfer for effective binding of O‐related species and proton–electron charge exchange in the hydrogen evolution reaction. The Cu‐supported Ni4Mo/MoOx shows an ultralow overpotential of 16 mV at a current density of 10 mA cm−2 in 1 m KOH, demonstrating the smallest overpotential, at loadings as low as 0.27 mg cm−2, among all non‐noble metal catalysts reported to date. Moreover, an overpotential of 105 mV allows it to achieve a current density of 250 mA cm−2 in 70 °C 30% KOH, a remarkable performance for alkaline hydrogen evolution with competitive potential for applications. [ABSTRACT FROM AUTHOR]

Abstract Although the lithium–sulfur redox flow batteries (Li–S RFBs) are promising candidates for large-scale energy storage application because of outstanding solubility of long-chain polysulfides and low cost of sulfur. Their implementation has been impeded by multiple challenges, especially the dissolution of intermediate lithium polysulfide (Li 2 S X) species into the electrolyte. Here, Al 2 O 3 particles decorated polypropylene separator (PP-Al 2 O 3) was investigated. The results show that the thermal stability and the electrolyte wettability of the PP-Al 2 O 3 separator are improved obviously. When the PP-Al 2 O 3 separator is used for Li–S RFB, the cyclic stability and rate capability of the battery are enhanced. The PP-Al 2 O 3 separators are effective in improving the initial discharge capacity of Li–S RFBs from 27.5 to 91.5 mAh g−1 at 6.25 mA cm−2. The reason could be ascribed to that the polar Al 2 O 3 coating not only alleviates the shuttle effect by chemical interaction and physical barrier, but also facilitates Li-ion migration by favorable electrolyte wettability. In addition, theoretical calculations reveal that chemical bonds are formed between Al 2 O 3 and Li 2 S X. This work provides the rational design strategy for functional separators at cell scale to effective utilizing of active sulfur and retarding of polysulfides, which offers the possibility of high energy density Li–S RFBs with long cycling life. Highlights • Al 2 O 3 layer can enhance the thermal stability and the electrolyte wettability. • PP-Al 2 O 3 separator is used as a shuttle inhibitor for Li–S RFBs. • Li–S RFBs using PP-Al 2 O 3 separator show excellent electrochemical performance. • The results of XPS show that the Li–O is formed between the Li 2 S X and the Al 2 O 3. • DFT calculations reveal the interaction between Li 2 S X and Al 2 O 3. [ABSTRACT FROM AUTHOR]

• Exploring the effects of Si/Al ratio and Cu/Al ratio on catalyst activity. • Researching the sensitivity of catalyst to aging time and aging temperature. • Explaining the reasons for the degradation of catalyst performance caused by hydrothermal aging. • Using in-situ DRIFTS experiments and DFT molecular simulation calculations to explore the mechanism. • Completing the hydrothermal aging mechanism of Cu-SSZ-13 small pore molecular sieve catalyst. A series of Cu-SSZ-13 small-pore molecular sieve catalysts are prepared by the ion-exchange method, analyzed, and tested by changing the synthesis ratio, and performing hydrothermal aging treatment under various aging conditions to explain the degree of influence. The investigations are carried out to reveal that when the Si/Al ratio is 10, the catalyst has the best comprehensive performance and ZCuOH sites are more prone to transformation and loss than Z 2 Cu sites during the hydrothermal aging process. In-situ DRIFTS experiments and DFT molecular simulation calculations are used to explain the reasons for the degradation of catalytic performance caused by the hydrothermal aging, which completes the study of the hydrothermal aging mechanism for Cu-SSZ-13 molecular sieve catalysts. The result shows that Z 2 Cu active sites exhibit better hydrothermal aging resistance than ZCuOH, the catalyst is more sensitive to aging temperatures than durations, and its limit of the aging temperature is about 850 ℃. [ABSTRACT FROM AUTHOR]

Aqueous zinc-ion batteries (ZIBs) stand out among the next generation of large-scale energy storage devices owing to their overwhelming advantages of high safety, low-cost and environmental benefit. However, this promising technology is still plagued by lack of superior cathode materials due to the inherent slow diffusion kinetics. Herein, with theoretical calculations as a guide, we proposed a new strategy to promote Zn2+ migration based on ion-exchange. Specifically, we first find the tendency of Mg2+ and Zn2+ exchange in inverse-spinel Mg 2 VO 4 by molecular dynamics simulations. Density functional theory (DFT) calculations reveal that this ion exchange can moderate the electrostatic interaction between Zn2+ and host material, and reduce the diffusion energy barrier of Zn2+. Meanwhile, the Mg2+ of host leaves vacancies when it is detached, and both contribute to the improvement of Zn2+ diffusion kinetics. Based on theoretical calculations, we for the first time used a simple sol-gel method to synthesize inverse-spinel Mg 2 VO 4 as an aqueous ZIBs cathode. As predicted in theoretical calculations, after optimization of Zn2+ and Mg2+ exchange, the Mg 2 VO 4 /Zn system demonstrates rewarding cyclic stability. This work provides a new insight into the development of cathode materials for high-performance ZIBs. • Theoretical calculations guide experiments. • An ion exchange mechanism is proposed. • The ion exchange mechanism is favorable for zinc ion diffusion. • Mg 2 VO 4 is evaluated as a cathode for zinc-ion batteries for the first time. • The ion-exchange optimized Mg 2 VO 4 shows excellent performance and applicability. [ABSTRACT FROM AUTHOR]

• Using DFT to explore the adsorption of gas molecules on catalysts surface. • Investigating the characteristics of catalytic active sites and reaction mechanisms through DFT. • Explaining the catalysts poisoning process through DFT. • Illustrating the catalysts hydrothermal aging process through DFT. • Catalysts modification and design based on DFT. In recent years, molecular simulation methods, especially density functional theory (DFT), have attracted much attention and been widely used to study the SCR reaction theoretically and microscopically. This review discusses the application of DFT in SCR research from the aspects of surface adsorption, active site characteristics, reaction mechanism, poisoning mechanism, and hydrothermal aging mechanism to illustrate the status of quantum chemical computing in this field. The gas adsorption includes the adsorption of nitrogen oxides, ammonia, and their co-adsorption. The site and mechanism include the properties of different active sites, intermediate species analysis, and reaction mechanism research. The poisoning includes related research on sulfur poisoning and alkali metal poisoning. The hydrothermal aging includes research on dealumination and loss of active sites. It is demonstrated that the catalysts can be improved and rationally designed based on quantum chemistry calculations. Finally, the application of DFT in this field is evaluated, hoping to provide good suggestions for DFT calculations to further understand the more complicated reaction mechanisms and optimally design the SCR catalysts. [Display omitted] [ABSTRACT FROM AUTHOR]