Based on DFT calculations at the PBE0-D3/def2-TZVP level, this study investigated the lowest energy structures obtained in this study of Ptn+(n = 3-9) clusters, water molecule adsorption on their surfaces, and the HER mechanism. Water molecules preferentially adsorbed at the top sites of all clusters (adsorption energies:-1.24 to-2.64 eV, exothermic), with Pt8+ and Pt9+ exhibiting the highest adsorption energies. For HER, the Pt7+ system required the fewest steps (only 2), while Pt8+ needed the most (9 steps). Pt3+-Pt7+ showed endothermic behavior (reaction energies: 0.41-1.91 eV), whereas Pt8+ and Pt9+ were exothermic (-0.47 eV and-0.71 eV, respectively), with Pt9+ having the most feasible pathway. Except for Pt7+, other systems formed Pt-H-Pt or Pt-O-Pt bonds; Pt3+/Pt4+/Pt7+ stayed stable, others distorted. This study provides a theoretical reference for designing high-efficiency Pt-based catalysts for water splitting.

Cyclo[n]carbons─molecular rings composed exclusively of sp-hybridized carbon atoms─represent a uniquely demanding frontier in carbon allotrope chemistry owing to their extreme structural sensitivity and unconventional π-electron behavior. The recent on-surface synthesis of cyclo[25] carbon (C25), the largest odd-membered ring realized to date, provides an unprecedented opportunity to interrogate the fundamental properties of electron-deficient, symmetry-broken carbon nanostructures. Here we combine extensive first-principles calculations─spanning ground-state electronic structure, magnetic response, and thermodynamic stability─to elucidate the bonding and antiaromatic character of C25. We show that C25 adopts a planar Cs-symmetric triplet ground state featuring pronounced bond-length and bond-angle alternation, reflecting a delicate interplay between Peierls distortion and electron delocalization. π-Electron analysis reveals a striking departure from even-membered cyclocarbons: the πin subsystem supports simultaneous clockwise and counterclockwise induced ring currents under an external magnetic field. This counterintuitive duality originates from the intrinsic phase discontinuity of odd-membered rings, wherein the πin wave function cannot achieve periodic phase closure and undergoes a π phase inversion between the inner and outer regions of the ring. ACID, NICS and ICSSZZ analyses collectively confirm that C25 is globally antiaromatic, with its unusual current patterns arising from phase-frustrated π conjugation rather than conventional Hückel-type electron counting. NICSZZ analysis of structures sampled from AIMD trajectories confirms the thermally robust weak antiaromaticity of C25 without aromaticity inversion. Excited-state calculations further show that the dominant absorption features stem from strongly localized π → π* transitions involving mixed contributions from both πin and πout manifolds. These results identify C25 as a phase-frustrated, open-shell cyclocarbon with structural and magnetic properties fundamentally distinct from those of even-membered homologues. The insights obtained here provide a basis for understanding antiaromaticity and excited-state behavior in odd-membered sp-carbon rings and may facilitate future studies of larger or functionalized cyclocarbons.

Hydrogen energy has garnered widespread attention as a clean energy source. This study employs density functional theory (DFT) to systematically investigate the hydrogen storage performance of Ben(n = 10-12) clusters. The results reveal that hollow spherical Ben clusters exhibit excellent hydrogen storage capacity while maintaining good thermal stability even after H2 adsorption at room temperature. Specifically, Be10, Be11 and Be12 clusters can adsorb 26, 28, and 30 H2 molecules, achieving hydrogen storage densities of 31.96 wt%, 31.87 wt%, and 35.87 wt%, respectively-far exceeding the U.S. Department of Energy's target of 5.5 wt%. Calculations indicate an average adsorption energy between 0.16 and 0.19 eV/H2, which lies between physisorption and chemisorption. IGMH isosurface analysis confirms the physisorption characteristics of H2 molecules. PDOS analysis reveals that the hydrogen storage mechanism primarily originates from H2 molecular polarization and van der Waals forces arising from orbital hybridization between hydrogen atoms and the substrate. Desorption temperature calculations show that, above 216 K, this material demonstrates potential for reversible hydrogen storage. This study demonstrates that these three hollow spherical beryllium cluster systems are ideal candidates for achieving ultra-high-capacity reversible hydrogen storage.

In this theoretical work, the Na atom doped cyclo[16]carbon complex is studied, and we finally obtained two stable configurations: Na@C16 and Na&C16, with Na atom inside and outside the ring, respectively. The calculation results show that an external electric field (EEF) can drive the transformation of the two conformations. Applying an appropriate EEF can adjust the relative energy of the two configurations and the rate of mutual transformation, thereby switching the dominant configuration of the NaC16 complex. So, it provides the possibility of the NaC16 complex as an EEF tunable switch. The first and second hyperpolarizabilities (static and frequency-dependent) of the two configurations are found to be significantly different, which indicates that the second-order and third-order nonlinear optical properties of the NaC16 complex can be effectively regulated by switching the location of doped Na atom between inside and outside the carbon ring. Therefore, the NaC16 complex under the EEF could be introduced as a promising molecular device.

Abstract In hydrocarbon fuel oxidation, propanal is a key intermediate and oxygenated pollutant. Its combustion rate constants are mostly estimated by analogy, bringing large uncertainties to kinetic models. This work comprehensively investigates H-abstraction from propanal by H/CH3/C2H5/OH radicals. High-precision rate constants and branching ratios were determined by multistructural variational transition state theory with small-curvature tunneling across 240–2000 K. Our findings emphasize that conformational flexibility and torsional anharmonicity greatly affect both the rate constants and branching ratios. Across the full temperature range, α-site abstraction (R1α) is the primary process in the propanal + H system. For propanal + CH3, the rate constant of β-site channel (R2β) is dominant. In the propanal + C2H5 system, the α-site reaction (R3α) remains prominent, whereas for propanal + OH, the branching ratios of the β-site and γ-site channels (R4β, R4γ) increase with temperature, while that of the α-site (R4α) decreases. Excellent agreement with available experimental data is achieved by the fitted expression kR4 = 0.0017 × T4.835 exp(2621.61/T) (in cm3 mol–1 s–1) for the total rate constant of propanal + OH. The new rate constants were adopted to update Veloo et al.’s kinetic model, followed by sensitivity analysis. The revised model enables more reliable simulation of propanal combustion and emission behaviors.

H-abstraction by reactive radicals OH, HO2, H, and CH3 governs diisopropyl ether (DIPE) oxidation kinetics, with preferential attack at α-carbon sites adjacent to the ether oxygen. Current kinetic models exhibit significant uncertainties due to scarcity of high-level experimental and theoretical data, necessitating rate estimation via structural analogs. To resolve these gaps, we employed high-accuracy multi-structural variational transition state theory with small-curvature tunneling correction (MS-VTST/SCT) coupled with M06-2X/cc-pVTZ//M08-HX/def2-tzvp (M08-HX/def2-tzvp is the combination with the smallest MUD value based on DLPNO-CCSD(T)/CBS(T-Q)) calculations. This approach systematically investigates H-abstraction across all carbon sites in DIPE + OH/HO2/H/CH3 systems. Activation energies of -0.62 to 22.69 kcal mol-1 reveal hydrogen-bonded complexes RCαOH and RCβ1HO2 stabilizing transition states in OH/HO2 pathways. Detailed analysis of temperature-dependent rate constants (200-1700 K) and branching ratios uncovers dominant torsional/anharmonic effects on microcanonical pathways: in DIPE + OH, (R1a) dominates below 550 K owing to hydrogen-bond-induced barrier reduction while (R1b) prevails at higher temperatures due to enthalpy advantage; (R3a) and (R4a) consistently control DIPE + H/CH3 consumption across combustion-relevant conditions. The total rate for DIPE + OH, ktotal = 0.1015 × T4.514 exp(-3457.125/T) cm3 mol-1 s-1, not only agrees excellently with experimental data but also reveals non-Arrhenius behavior above 450 K. Implementation of these first-principles rates in an updated combustion model substantially improves predictions of CH3COCH3. C3H6 and C2H6 species profiles in jet-stirred reactor experiments at φ = 1.0, 1 atm. Reaction pathway analysis further quantifies H-abstraction as the primary DIPE consumption route, contributing >75% fuel depletion below 900 K.

The unique electronic properties of cyclo[N]carbon have attracted considerable attention due to their potential applications in gas storage and sensing technologies. This work employed density functional theory (DFT) and DLPNO-CCSD(T) to investigate the molecular adsorption characteristics of cyclo[N]carbon (N = 12, 14, and 16) with various gas molecules. It is interesting that the adsorption strength of cyclo[N]carbon for gases increases as the size of cyclo[N]carbon increases, with polar molecules demonstrating stronger interactions than nonpolar ones. Local energy decomposition analysis at the high-end DLPNO-CCSD(T) level of theory reveals that London dispersion forces significantly contribute to adsorption stability. By incorporating the Mg2 dimer in two-layer C16, a stable Mg22+@(C16)22- complex is formed, and the encapsulation of divalent cations considerably enhances the gas molecule adsorption performance. This study provides valuable insights into the adsorption properties of cyclo[N]carbon, which could be crucial for advancements in next-generation molecular devices.

This work presents a regulation effect of external electric fields on geometric structures, spectral properties, and reaction activity of (ZnSe) n (n = 3 and 6) on the basis of density functional theory. The results show that the external electric field has a regulatory effect on all aspects of (ZnSe) n (n = 3 and 6). The external electric field can change the shape of (ZnSe)3 from a plane to three-dimensional and stretch (ZnSe) n (n = 3 and 6) along the direction of the electric field and induce a significant dipole moment transformation (direction and magnitude). This is mainly attributed to the polarization of atoms under the external electric field, which leads to the movement of charges and the movement of charged atoms due to the force. Additionally, the EEF can lower the HOMO-LUMO gap and regulate the UV-vis spectra to form new absorption bands in the visible or near-infrared range, and thus enables (ZnSe) n (n = 3 and 6) to display color, and is hopeful to regulate the (ZnSe) n (n = 3 and 6) to present different fluorescence emission wavelengths. Finally, theoretical calculations reveal that the EEF can change the distribution of electrophilic or nucleophilic reaction sites of (ZnSe) n (n = 3 and 6). In view of the structural deformation and characteristic change of (ZnSe) n (n = 3 and 6) under the EEF, designing deformable materials driven by EEF is promising, and it is foreseeable that semiconductor clusters with different properties can be designed to be adjusted according to the strength and direction of the applied EEF.

The recent breakthrough in synthesizing cyclo[13]carbon (C13), an odd-membered all-carbon ring system, represents a significant advancement in developing nontraditional carbon allotropes with reduced structural symmetry. In this study, we systematically investigated the thermal stability, geometric structure, and electronic properties of C13 using first-principles calculations. Our results show that the C13 exhibits lower thermal stability due to its low symmetry. Notably, the π-electron delocalization is significantly enhanced over its shorter C─C bonds. Electrostatic potential (ESP) and average local ionization energy (ALIE) mapped on the van der Waals (vdW) surface of C13 reveal considerable spatial heterogeneity, arising from intrinsic variations in bond lengths and bond angles within the ring. Magnetic response analysis further identified a counterclockwise ring current in C13, consistent with its doubly antiaromatic electronic configuration. Additionally, the excitation process of C13 displayed mixed excitation characters, which should be regarded as a highly localized π-π* type of excitation. These comprehensive theoretical insights advance the mechanistic understanding of experimental observations in C13 and provide a foundational framework for investigating electron-deficient antiaromatic systems in carbon-rich molecular architectures.

In this study, density functional theory (PBE0-D3/def2-TZVP) were used to study the reaction mechanism of magnesium clusters (Mgn, n = 9-12) with the hydrolysis of monohydrate molecules. Through Structural optimization and transition state analysis, stable cluster structures and reaction pathways were elucidated. It was found that all Mgn clusters (n = 9-12) can spontaneously generate H2 upon reacting with water molecules, releasing energy up to 3 eV, with Mg12 exhibiting the optimal performance due to its low symmetry and high active site density. Further analysis revealed that H2 adsorption is dominated by van der Waals forces, indicating physical adsorption, while the formation of Mg-O bonds drives hydrogen generation. Notably, charge transfer becomes more significant in larger-sized clusters. These findings provide theoretical guidance for designing efficient magnesium-based catalysts and shed light on the structure-activity relationship between cluster size and reactivity, holding implications for developing novel materials for hydrogen production.

Dibutyl ether, with a cetane number around 100 and high combustion stability, is a promising candidate for diesel fuel replacement. Reaction path analysis indicates that H-abstraction dominates the early stages of dibutyl ether combustion. To enhance understanding of dibutyl ether's oxidation chemistry, this study systematically investigates H-abstraction processes of small molecular radicals (CH3, HO2, and OH). DLPNO-CCSD(T)/CBS(T-Q) was employed as a benchmark, and the performance of various density functionals was evaluated with different basis sets. The M08-HX/cc-pVTZ method, characterized by a mean unsigned deviation of 0.63 kcal/mol, was chosen for direct kinetic calculations. Rate coefficients for dibutyl ether + CH3/HO2/OH reactions at 200-2000 K were determined through the application of canonical variational transition state theory integrated with small curvature tunneling. The branching ratios reveal competition between C alpha and C delta within the reactions of dibutyl ether with HO2 and OH radicals at elevated temperatures, with C alpha dominating as temperatures decrease. For dibutyl ether + OH, the expression for the total reaction rate coefficient is as k = 1.93 x 10- 2 T4.97 exp (589.65/ T) (cm3mol- 1s- 1), showing good agreement with experimental data. The calculated H-abstraction rate coefficients were incorporated into a previously proposed model. The modified model shows significant improvements in species concentration evolution in a jet-stirred reactor and ignition delay time predictions, outperforming the original model in matching experimental results.

Elucidating the combustion chemistry of pentanone isomers provides critical insights into the reaction pathways of complex fuels and ketones with more than five carbon atoms. This study investigates the influence of OH and CH3 radicals in the oxidation processes of pentanone isomers, employing multi-structural variational transition state theory in conjunction with small curvature tunneling effects to calculate H-abstraction rate constants and branching ratios for the 2-pentanone (MPK) + OH/CH3 and 3-pentanone (DEK) + OH/CH3 reaction systems across a temperature range of 200-1500 K. The findings reveal that multi-structural torsional anharmonicity significantly influences reaction rate constants and branching ratios, thereby altering the importance attributed to different reaction channels. In the MPK + OH system, the carbonyl group's interaction with the transition state of reaction R1 beta, through hydrogen bonding, reduces the reaction barrier, rendering R1 beta the dominant pathway. For the MPK + CH3 system, multi-structural torsional anharmonicity leads to channel competition, with R2 alpha prevailing between 210-1400 K. In the DEK + OH system, R1*alpha takes precedence at temperatures exceeding 220 K. The total rate constants for the MPK + OH and DEK + OH systems, derived from our calculations, are presented with excellent agreement to the measurements, affirming the reliability of our computational approach. The specific expressions for these rate constants, are delineated as follows: k R 1 = 0.0160 x T 4.599 exp (1916.431/ T ) and k R * 1 =18.1368 x T 3.714 exp (1128.475/ T ) (cm3mol-1sec-1). Utilizing the computed rate constants, the Pieper, Kang, and Lin kinetic models are refined, enhancing the simulation accuracy of ignition delay times and species concentrations. Sensitivity analyses have been conducted to identify the pivotal reactions within the oxidation processes of MPK and DEK.

Due to the limitations of comprehensive experimental and theoretical research, rate coefficients are commonly derived through analogies with alcohols or estimations based on alkane data. Consequently, this paper delves into the critical H-abstraction reactions involving n-hexanol and radicals (H, HO2, OH and CH3), serving as foundational steps in the combustion mechanism. Rate coefficients are determined using traditional and variational transition state theory combined with Eckart tunneling correction. Emphasis on H-abstraction from C alpha is evident in branching ratios for n-hexanol + H/HO2/CH3 systems, while the dominant reaction for n-hexanol + OH system shifts from C epsilon above 330 K to C beta below 330 K. The total H-abstraction rate coefficient for n-hexanol + OH is calculated as k OH = 12.76 x T3.62 x exp. (472.81/T) (cm3mol-1 s-1), with the CBS-QB3 level reproducing experimental data commendably. Furthermore, the kinetics model proposed by Togb & eacute; et al. is refined through updated rate coefficients, validated against ignition delay times, showcasing notable agreement with experimental data. Reaction path and sensitivity analyses provide insights into crucial reactions and corresponding fuel consumption paths during n-hexanol oxidation.

The conventional method of producing hydrogen does not promote sustainable development and gravely damages the environment. Nevertheless, this paper studies investigate the connection between the magic numbers (4, 10, 17) and the reactions of Ben(n n (n = 14-17) clusters splitting H2O 2 O to produce H2 2 as well as the reaction mechanism, solving the environmental pollution problem. This experiment reveals the mechanism of hydrogen generation from H2O 2 O splitting of Ben n (n = 14-17) clusters using the PBE0 functional and the def2-TZVP basis, which is based on density functional theory. We have plotted the energy gap diagrams, interaction region indicator diagrams, and density of state diagrams of Ben(n n (n = 14-17) clusters in order to explore the intermolecular interactions and energy changes that occur during the adsorption and desorption of water molecule and clusters. The findings demonstrate that the reactions of Ben(n n (n = 14-17) clusters splitting H2O 2 O to produce H2 2 is releasing energy. The Ben(n n (n = 14-17) clusters have the best hydrogen evolution efficiency when the number of atoms is near the magic number.

This study addresses the global rise in energy demand and the environmental challenges posed by fossil fuel usage, such as greenhouse gas emissions and pollution. It explores the potential of cluster catalysts, specifically gallium (Ga) and beryllium (Be) clusters, for splitting water molecules to generate hydrogen. Using density functional theory (DFT), we conducted an in-depth analysis of the interactions between Ga5 and Ga4Be clusters with water molecules and the mechanisms of hydrogen production. The results indicate that while Be doping slightly reduces the binding energy and structural stability of the clusters, it significantly decreases the band gap, promoting electron transfer and enhancing catalytic activity. Adsorption energy calculations reveal that Be doping notably increases the adsorption strength of water molecules on the cluster surface, particularly through the formation of Be-O chemical bonds. This enhanced adsorption effect facilitates the breaking of O-H bonds in water molecules, significantly lowering the reaction energy barrier and transforming the process from an energy-driven to a spontaneous exothermic reaction. Furthermore, the resulting hydrogen molecules are adsorbed on the cluster surface through van der Waals forces, making them easy to desorb. This indicates that the catalytic system is highly efficient in hydrogen production and holds strong potential for practical applications.

The nanographene with negative curvature has been extensively studied due to its interesting properties and potential applications. In the present work, we have performed all-electron scalar relativistic density functional theory (DFT) calculations to understand the periodic interaction mechanisms of actinide atoms (An = Th, Cm) with the TB8C nanographene. The encapsulated complexes (An@TB8C) were formed due to the octagonal vacancy in the TB8C nanographene. TB8C shows fairly high affinity toward An atoms, especially for Th and Pa. AIMD simulations further confirmed the effective trapping of An atom with TB8C. The partial covalent characters of An-C bonds in An@TB8C were revealed through various bond analysis methods. The 6d electrons of An play an important role in the participation of chemical bonds. The delocalization index (DI) is proposed as a useful descriptor in the study of bond strength involving the actinides. Electronic absorption spectra were simulated for further identification in the experiments. The current work has expanded the potential molecular properties and applications of nanographene.

n-Pentanol is acknowledged as a prospective alternative and a supplement to traditional fossil fuels. H-abstraction reaction assumes a pivotal role in initiating the chain reaction during n-pentanol combustion. To investigate the oxidation characteristics of n-pentanol, the composite quantum chemical methods CBS-QB3 and G4 are employed to obtain thermochemical and kinetic parameters in the H-abstraction reaction of n-pentanol. The calculated isobaric heat capacity provides accurate predictions of the experimental results. Branching ratios underscore that H-abstraction at the C-alpha site serves as the primary channel between n-pentanol and (H) over dot/(C) over dotH(3)/(O) over dotH(2). For the reaction between n-pentanol and (O) over dotH, the C-beta site emerges as the most favorable channel due to the significant variational effect. The overall rate coefficient for H-abstraction from n-pentanol by (O) over dotH radicals is expressed as k = 3565.11 x T-2.93 exp (1465.44/T) (cm(3) mol(-1) s(-1)), and the data obtained at the CBS-QB3 level demonstrate good agreement with experimental observations. Furthermore, the original model is modified based on current results, and the improved model demonstrates superior predictive capabilities for jet-stirred reactor (JSR) data and ignition delay times. Reaction path and sensitivity analyses are employed to identify fuel consumption pathways and critical reactions in the combustion of n-pentanol.

Density functional theory calculations are performed to analyze the structure and stability of Cu and Cu-K clusters with 3 to 9 atoms. The results indicate that the stability of the clusters decreases after doping with a K atom. With the increase of cluster size, the stability of the clusters shows odd-even alternation. Cu-8 and Cu7K clusters exhibit the highest stability. Next, different adsorption sites are considered to investigate the geometry of CunNO and Cun-1KNO clusters. By calculating the adsorption energy and the HOMO-LUMO energy gap, it is determined that both types of reactions are exothermic processes, indicating stable adsorption of NO. Notably, the CunK clusters are more active (stronger adsorption) for NO than the Cu-n clusters. The most chemically active clusters among CunNO and Cun-1KNO clusters are Cu8NO and Cu7KNO clusters. Finally, electron transfer and Mayer bond order analysis of Cu8NO and Cu7KNO clusters reveal that the NO bond order decreases due to electron transfer when Cu/Cu-K clusters adsorb NO. In this process, the N atom is the electron donor and the Cu atom is the electron acceptor. Fundamental insights obtained in this study can be useful in the design of Cu/Cu-K catalysts.

In this study, first-principles calculations were used to conduct in-depth studies on multiple key aspects of N-doped defective graphene modified with Mg atoms, including structure, electronic property, thermal stability, as well as hydrogen storage performance and mechanism. The research results show that after the introduction of Mg, N atoms and vacancy defects, pristine graphene transforms from semi-metallic property to metallic property. And the AIMD results indicate excellent thermodynamic stability of the substrate. It can adsorb up to seven H2 molecules, and the adsorption energy values is between -0.15 and -0.21eV, which is in the stable energy range (-0.15 to -0.60eV). The hydrogen storage mechanism is mainly attributed to the van der Waals force caused by the polarization of H2 molecules and orbital hybridization between H atoms and the substrate. The calculation of the desorption temperature shows that this substrate can become a potential candidate for reversible hydrogen storage materials at temperatures above 206 K. Compared with graphene decorated with Mg atoms, the introduction of N atoms and vacancy defects significantly improved the hydrogen storage performance.