Reactive Force Field Molecular Dynamics Research Articles

Formation mechanism of soot in pyrolysis of 2-methylfuran under high temperature based on ReaxFF molecular dynamics simulation

In this study, the detailed mechanism of soot formation under high temperature pyrolysis of 2-methylfuran (2-MF) has been investigated by using Reactive force field molecular dynamics (ReaxFF MD) simulation. The MD analysis shows that 2-MF undergoes ring cleavage and the removal of CO/HCO/CH2CO/CH3CO, which results in the production of the C2-C4 species, promoting the formation of the initial ring molecules. The clustering of hydrocarbons by radical-chain reaction (CHRCR) mechanism plays a significant role in the mass growth of both polycyclic aromatic hydrocarbons (PAHs) and initial soot particles. The main contributors to this process are C2H2 and resonance-stabilized free radicals of C3 and C4. The H-abstraction-C2H2-addition (HACA) mechanism is important for the formation of surface active sites for PAHs and initial soot to some extent. In addition, the soot formation capacity of 2,5-dimethylfuran (25DMF) and 2-MF are compared. Under the same simulation conditions, 25DMF exhibits a higher capacity to form soot. Compared with 2-MF, 25DMF pyrolysis forms more ring-containing species at the initial stage, particularly cyclopentadiene and its derivatives. These compounds have the ability to promote the formation of PAHs, thus providing further support to the experimental-based theory.

Evaluation of the synergistic effect of platinum-supported graphene materials on methylcyclohexane decomposition via flow reactor experiments and reactive force-field molecular dynamics simulations

Hydrogen technology is a viable alternative to carbon-based energy sources. However, the widespread use of hydrogen energy is limited by its low volumetric energy density, complex supply chain, and difficulties related to hydrogen storage. This study investigates the influence of Pt-supported graphene additives on hydrogen formation and decomposition of methylcyclohexane (MCH), which is a potential hydrogen carrier, by conducting high-pressure liquid flow reactor experiments and reactive force-field molecular dynamics simulations. This investigation represents a notable improvement in the MCH decomposition and hydrogen generation efficiencies through enhanced catalytic dehydrogenation facilitated by Pt-decorated functionalized graphene sheets (Pt@FGSs). Experimental results indicate that under fixed reaction conditions, the bicomposite structure of the Pt@FGSs at a loading concentration of 50 ppmw reduces the dehydrogenation energy and increases the conversion rate by up to 45%. The yields of products such as hydrogen and low-carbon species are also significantly improved. Notably, hydrogen formation is enhanced by a factor of approximately 2, demonstrating the effectiveness of Pt@FGSs in facilitating fuel decomposition and promoting hydrogen production. In addition, reactive force-field molecular dynamics simulations elucidate possible enhancement mechanisms, in which Pt nanoparticles attach to FGSs and catalyze the dehydrogenation of MCH and its derivatives. The production of a higher amount of the produced hydrogen is evidenced by the desorption of H atoms attached to the Pt surface. This study provides valuable insights that can accelerate the transition towards sustainable and effective decarbonization strategies using MCH as a hydrogen carrier.

Methanol-assisted NO oxidation under an oxygen atmosphere for efficient denitration: Experiments and ReaxFF-MD simulations

The development of selective catalytic reduction technologies for controlling nitrogen oxide (NOx) emissions in flue gas is hampered by high equipment and catalyst costs. In this study, a catalyst-free and efficient denitration process using methanol and oxygen as reactants was developed. Various gas atmospheres with differing concentrations were investigated to remove NO without catalysts. The addition of methanol significantly enhanced NO removal efficiency, reaching 94.6 % at 550 °C, with 55.1 % of NO converted to NO2, which can be absorbed by downstream alkali solutions. Reactive force field molecular dynamics (ReaxFF-MD) simulations were employed to analyze the atomic level NO oxidation mechanism in the CH3OH/NO/O2/H2O homogeneous reaction system. The simulation revealed the generation pathway of three key oxidizing intermediates (OH, HO2, and H2O2) and their roles in NO oxidation. This study offers critical insights into developing a cost-effective denitration process, highlighting the potential for improved NOx emission control.

Soot formation and laminar combustion characteristics of anisole: ReaxFF MD simulation and kinetic analysis

The application of biomass energy is one of the important ways to achieve carbon neutrality and deal with global warming. The study on the combustion mechanism of anisole, an oxygen-containing fuel, is helpful for biofuel large-scale application. In this study, the soot formation and laminar combustion characteristics of anisole were analyzed by reactive force field molecular dynamics (ReaxFF MD) and kinetic simulation, respectively. ReaxFF MD simulation studies had shown that soot formation of anisole combustion occurred in three stages, stage 1 (0–1 ns), stage 2 (1–2.5 ns), stage 3 (2.5–6 ns). The three stages represented the pyrolysis of the fuel, the developmental stage of the soot, and the graphitization stage of the soot, respectively. During the combustion of anisole, primary mechanisms for the soot formation were as follows: H-abstraction-C2H2-addition, carbon-addition-hydrogen-addition, internal ring formation and long carbon chain link. The formation of soot graphitization exhibited different morphologically behaviors: from flakes to onions to spheres with fewer branched chains. From the study of the laminar combustion characteristics of anisole, it can be found that the laminar burning velocities increased along with the increase of temperature, while the opposite trend was shown along with the increase of pressure. The sensitivity coefficient of naphthalene, the main soot precursor, revealed that the main promotional reactions for soot formation were R5 (O2 + H < = > O + OH), R36 (CO + OH < = > CO2 + H).

Effects of oxidizer concentration and abrasive type on interfacial bonding and material removal in 4H-SiC polishing processes.

Determination of chemical effects involved in material removal during the polishing process of 4H-SiC has been a challenge. In this study, the polishing processes of 4H-SiC under the action of diamond and SiO2 abrasive in different concentrations of H2O2 solutions are investigated by reactive force field molecular dynamics simulations. It is found that 4H-SiC can be oxidized by H2O2 solution at the atomic scale, but the chemical reaction alone does not lead to material removal. An increase in the concentration of H2O2 solution and the mechanical action of abrasives can promote the oxidation of 4H-SiC. Since the mechanical removal dominates material removal when polishing 4H-SiC with diamond abrasive, there is no clear pattern in the effect of H2O2 solution concentration on material removal. Nevertheless, the removal of atoms associated with chemical bonds dominates material removal when polishing 4H-SiC with SiO2 abrasive. Therefore, the damage and atomic removal of 4H-SiC are lower. Since the H2O2 solution can increase the total number of bonds between 4H-SiC and SiO2 abrasive, an increase in the concentration of H2O2 solution can improve the material removal rate. These findings can provide guidance for the 4H-SiC polishing process in terms of abrasive and oxidizer selection.

Unraveling the reaction mechanism of alkali-activated materials through multi-scale modeling

As an environmentally friendly alternative to cement-based materials, alkali-activated materials (AAM) have attracted much attention due to their significant ability to reduce greenhouse gas emissions and effectively utilize industrial waste. Three Si-Al monomers ([SiO2(OH)2]2-, [SiO(OH)3]-, and [Al(OH)4]-) serve as the fundamental building blocks for the formation of AAM gels. Simulating their polycondensation reactions (PR) among these monomers is of paramount importance but faces a delicate balance between precision and efficiency. To unravel the PR mechanisms, we have integrated reactive force field molecular dynamics (MD) simulations with first-principles calculations based on density functional theory. Our 100ps MD simulations reveal that Al monomers exhibit faster reaction rates and lead to the formation of Si-Al oligomers with diverse structures. Subsequent first-principles calculations on transition state models derived from MD results uncover that PR pathways involving Al monomers possess lower energy barriers, which are correlated with changes in chemical bond strength arising from electronic orbital transitions. Our study, for the first time, establishes an intrinsic link among five hierarchical levels: electronic orbital structure, chemical bond strength, reaction energy barrier, reaction rate, and reaction scale. This provides invaluable theoretical guidance for designing energy-efficient and low-barrier reaction pathways for AAM gel formation.

Insight into the mechanism of H2O promoted CaCO3 decomposition in CO2 atmosphere

Calcium looping is one of the most promising CO2 capture technology. The flus gas during the calcination stage of the calcium looping contains both CO2 and H2O. However, the effect of H2O on the decomposition of carbonation in the CO2 atmosphere remains inconclusive. This study employed the Reactive Force Field molecular dynamics (ReaxFF-MD) simulations to investigate the influence of H2O on the decomposition of calcium carbonate in a CO2 atmosphere. The TGA experiments demonstrated that H2O increases the decomposition rate of calcium carbonate and also reduces the reaction temperature. Subsequently, the effects of varying CO2 and H2O concentrations on the decomposition of calcium carbonate were examined using ReaxFF-MD simulations. The simulation results for calcium carbonate decomposition, with the addition of CO2 and H2O, aligned with the experimental trends, verifying the reliability of the models. By tracking and labeling carbon, oxygen and hydrogen atom sources in the simulation, the decomposition, carbonation and hydrolysis reaction network for the CaCO3 decomposition in CO2 atmosphere was systematically constructed. Analysis of the chemical reactions and atomic distribution indicated that H2O primarily facilitates calcium carbonate decomposition by generating HCO3− through surface hydrolysis, which reduces the activation energy of the reaction. Moreover, the hydroxyl groups formed by hydrolysis compete with atmospheric CO2 for active sites on CaO, further inhibiting the carbonation reaction and increasing the calcination rate.

ReaxFF molecular dynamics study of N-containing PAHs formation in the pyrolysis of C2H4/NH3 mixtures

The reactive force field molecular dynamics (ReaxFF MD) simulations are performed to depict the whole process including fuel pyrolysis, the formation and growth of PAHs/NPAHs and soot formation in the pyrolysis of C2H4 and C2H4/NH3 mixtures. NH3 doping increases the concentration of H radicals through the decomposition of NH3. These H radicals then promote the consumption of C2H4 by participating in H-abstraction reactions. The formation of C-N species (mainly HCN, H2CN, C2N, CH3CN, NCCN, and HC3N) removes the C atoms participating in the formation of PAHs and soot, thus inhibiting the formation of soot. And such inhibitory effect is strengthened with increasing temperature due to the promoted formation of C-N species. Most importantly, the structure, formation and evolution paths of N-containing PAHs (NPAHs) are identified based on the experimental and simulation results for the first time, revealing that N atoms in the NPAHs are almost always present in the carbon chains attached to the aromatic rings while barely enter the rings to form heterocyclic structure. The simulations further reveal that when the temperature is less than 2500 K, the first N-containing aromatic ring is formed through the reaction of phenyl with small C-N species (such as HCN and CN radicals), followed by the increase of new rings primarily via the HACA mechanism. At temperatures greater than 2500 K, the formation and growth of NPAHs are dominated by the continuous attachment of N-containing carbon chains and cyclic polycondensation-cyclization reactions. The identification of new C-N species especially NPAHs would help improve the kinetic mechanisms for ammonia blending combustion.

Pyrolysis mechanism of 1,1,1,2-tetrafluoroethane and 1,1,1,2-tetrafluoroethane/carbon dioxide as working fluids for transcritical power cycles: Insights from reactive force field molecular dynamics and density functional theory studies

Carbon dioxide-based mixtures in transcritical power cycle systems can enhance thermodynamic performance but may pose risks of thermal decomposition, potentially compromising system performance and safety. This study investigates the pyrolysis mechanism of 1,1,1,2-tetrafluoroethane (R134a)/carbon dioxide (CO₂), a typical CO₂-based mixture, using reactive force field molecular dynamics (ReaxFF-MD) simulations and density functional theory (DFT). ReaxFF-MD simulations are conducted at pressures ranging from 4 to 12 MPa and temperatures between 1800 K and 3200 K for various fluid compositions, including pure R134a and R134a/CO₂ mixtures at mole ratios of 0.7/0.3, 0.5/0.5, and 0.3/0.7. The effects of temperature, pressure, and composition on the thermal decomposition of both pure R134a and R134a/CO₂ mixtures are examined, with particular focus on behavior at 8 MPa. In the thermal decomposition of R134a/CO₂ mixtures, CO₂ inhibits the formation of F radicals and reduces their concentration through chemical reactions, thereby suppressing R134a decomposition. Pure R134a decomposes into primary products such as hydrogen fluoride (HF), fluorine (F), tetrafluoroethylene (C2HF4), trifluoromethyl radicals (CF3), and diatomic carbon (C2). The addition of CO2 results in the formation of additional products, including carbonyl fluoride (COF), oxygen (O), hydroxyl (HO), and formyl radicals (CHO). The decomposition pathways involve two reaction types: self-decomposition reactions dominate initially, while extraction reactions become more prominent later. Using the DFT approach, reaction energy barriers are analyzed to corroborate the ReaxFF-MD simulation findings. Moreover, the apparent activation energies for these reactions are quantified using first-order kinetics based on the Arrhenius equation, indicating that the thermal decomposition of R134a/CO2 mixtures is more challenging than that of pure R134a.

Study of the proton transfer during acidification of sodium salicylate based on ReaxFF molecular dynamics simulation

Salicylic acid(SA) is known for its pain-relieving and fever-reducing abilities and has a very broad range of applications, being an important ingredient in a wide variety of products such as pharmaceuticals, skin care products, agrochemicals, dyes, colorants, preservatives, and more. SA is mainly synthesized by the Kolbe-Schmitt method in industrial production, but there is still no standardized description of the mechanism of this reaction. The Kolbe-Schmitt reaction mechanism is divided into three steps, and the reaction mechanism of the first two steps has been fully investigated, while the reaction mechanism of Sodium salicylate (SS) acidification, as the last step in the synthesis of SA by the Kolbe-Schmitt process, has not been investigated, so we used the Reactive force-field molecular dynamics simulation (ReaxFF MD) method to simulate and reveal the reaction mechanism of the mixed solution of SS and sulfuric acid, followed by an orthogonal design to explore the effects of different factors on the yield of SA. Through the investigation, it was found that the reaction of SS with sulfuric acid mixed solution was divided into the following four stages in total: hydration reaction, proton transfer reaction, association reaction and dissociation reaction, respectively. It is concluded that the SA yield in SS acidification reaction is affected by the factors in the following order: concentration > pressure > time > temperature, where concentration and pressure significantly affect the SA yield. It is hoped that the present study can supplement the relevant understanding of the reaction mechanism of the Kolbe-Schmitt process, and at the same time have some practical significance and application value for the improvement and optimization of the synthetic SA process.

Analysis of the nanostructure evolution of soot in n-heptane/iso-octane with 2,5-dimethylfuran addition: A combined experimental study and ReaxFF MD simulations

The soot formation of n-heptane/iso-octane doped 2,5-dimethylfuran (DMF) with different ratios was experimentally investigated through laminar diffusion flame and numerically simulated by using the pyrolysis simulations method of reactive force field molecular dynamics (ReaxFF MD). The results showed that the laminar diffusion flame height of n-heptane/iso-octane increased with increasing DMF doping ratio. At a consistent sampling height, the primary soot particle sampling numbers collected were first decreasing and then increasing, and the size of the primary soot particle was first increasing and then decreasing accompanied by the DMF doping ratio increasing. Furthermore, the transmission electron microscope (TEM) analysis provided that DMF initially inhibited and subsequently promoted the primary soot particle growth in the n-heptane/iso-octane flame. The core-shell ratio increased and then decreased with the increase of the DMF doping ratio, which indicated that the maturity of soot decreased and then increased. In n-heptane/iso-octane doped with DMF ReaxFF MD pyrolysis simulation, it was divided into three stages 0–0.5 ns (the first stage), 0.5–3 ns (the second stage), and 3–4.5 ns (the third stage). Fuel decomposed in the first stage and reacted violently in the second stage. The soot precursors continued to react, molecule size kept to increase, and the polycyclic aromatic hydrocarbons (PAHs) continued to grow. In the third stage, the carbon number of the largest molecules were slowly increasing, and the development of soot entered mature stage, where the H/C ratio was slowly decreasing. Through ReaxFF MD simulations, it was found that the maturity of soot exhibited decreasing and then increasing trend with the increase of DMF doping ratio. The graphene-like structures were mainly concentrated around the H/C ratio of 0.297 region.

The dissolution of metal carbonate precipitation under the external electric and magnetic fields: reactive force field molecular dynamics simulation

Abstract The dissolution of metal carbonates holds a pivotal role in diverse industrial processes, environmental occurrences, and geological formations. Grasping the fundamental mechanisms underlying these processes is imperative for enhancing industrial applications and mitigating environmental impacts. Herein, we undertake a thorough investigation employing reactive forcefieldmolecular dynamics simulations to delve into the dissolution process of metal carbonates. These simulations afford profound insights into the mechanisms and kinetics governing the process across various conditions, encompassing temperature, acidity, and external electric and magnetic fields. Although temperature itself exerts a limited influence, the study reveals a synergistic enhancement of metal carbonate dissolution kinetics when temperature is combined with static electric and magnetic fields. Our revelations offer enlightening perspectives on the intricate interplay of factors shaping dissolution processes, laying the foundation for future inquiries in this domain.

Thermal stability of MDM and oxidative decomposition mechanism under the condition of air infiltration: A combined experimental, ReaxFF-MD and DFT study

When siloxanes are used as the working fluids of organic Rankine cycle systems, there is a possibility of air infiltration due to the large vacuum present in the condenser. To address this issue, experimental and simulation studies were conducted on the thermal stability and pyrolysis product characteristics of octamethyltrisiloxane (MDM) in the presence of air. The results indicated that air significantly promotes the decomposition of MDM at the temperatures above 250 °C. Air was helpful in increasing the formation of CH2O, CO, and CO2, and also enhanced polymerization of decomposition product of siloxane, leading to higher yields of MD2M, MD3M, MD4M, D3, D4, and D5. By combining reactive force field molecular dynamics (ReaxFF-MD) simulations with density functional theory (DFT) calculations, the microscopic mechanisms of MDM's oxidative decomposition by O2 in air and H2O under humid conditions were elucidated. O2 can easily combine with unsaturated Si atoms to form Si-O bonds, combine with CH3 radicals to form C-O bonds, and undergoes hydrogen extraction reactions to initiate decomposition. H2O mainly undergoes initial decomposition through CH3 radical hydrogenation and binding with unsaturated Si atoms. The generated O2H, O, and OH radicals tend to bind with Si atoms in molecules and radicals, facilitating polymerization reactions.

Kinetic insight of multi-molecule adsorption behaviors into the anticorrosion performance of azole inhibitors: A reactive force field molecular dynamics study

Density functional theory (DFT) calculations and molecular dynamics (MD) simulations are established as powerful tools in understanding the anti-corrosion mechanism of inhibitors at the atomic scale. Despite their widespread popularity, DFT calculations typically focus on small adsorption models while the inhibition efficiency of inhibitors is determined by multi-molecule adsorption film on metal surface. Classical MD simulations neglect the formation of chemical bonding, which frequently governs the overall adsorption process. In this contribution, reactive force field (ReaxFF) MD simulations were employed to overcome these limitations and investigate the differences in inhibitory capabilities among three classic azole compounds: imidazole (IDZ), 1,2,4-triazole (TAZ), and benzotriazole (BTA) on copper. Electrochemical tests and microscopic observations revealed that BTA demonstrated superior inhibitory effect on copper corrosion compared to IDZ and TAZ. However, the widely used descriptor, adsorption energy (Eads) in DFT calculations for predicting the inhibition ability of inhibitors were very similar, failing to explain the enormous variation in inhibition effectiveness. To explain this disparity, multi-molecule adsorption kinetics based on ReaxFF simulations were conducted. The results showed that BTA consistently demonstrated faster and more frequent adsorption on copper surface compared to the other two. The significant variance in inhibitory efficiency among the three inhibitors was elucidated for the first time from the kinetic insight.

Advanced computational modelling for biofuel catalyst optimization: enhancing beta zeolite acidity for oleic acid upgrading

We explore here, through reactive force field (ReaxFF) molecular dynamics simulations, oleic acid upgrading on beta zeolite (BEA) regulated with nine silica-to-aluminium ratios (SARs) to investigate their acid-catalyzed deoxygenation and coking susceptibility. The selected computational descriptors involved conversion, hydrodeoxygenation, and decarboxylation/decarbonylation selectivity, biofuels yield, and coke deposition characteristics. Simulations were validated by 20.3 SAR available experimental data and used for the systematic study. High deoxygenation selectivity was found to be related to the structural sensitivity of BEA(100) on the upgrading mechanism. ReaxFF simulations revealed that altering the Al-substitution could greatly promote biofuel formation. Specifically, SARs towards the mid-region (SAR 47) favored gasoline production, while 31 SAR exploited diesel-like hydrocarbons. An optimum ratio of 37.4 SAR achieved maximum oleic acid conversion (69.8%), with high yields of gasoline and diesel fuels (15.6 and 20.4 wt%, respectively) and moderate coking (8.6 wt%). Density functional theory screening of metallic dopants allowed investigating of their deoxygenation and coke susceptibility, obtaining that Cu-BEA structure favored the optimal carbon and O-moiety adsorption (-3.89 and -1.8 eV, respectively). Furthermore, the economic and environmental analysis showed that Cu-dopped BEA displayed the lowest market price and global warming potential (71 USD/kg and 2.8 kg CO2-eq/kg).

Reactive molecular dynamics simulations of poly(vinyl alcohol) gasification in supercritical carbon dioxide

Supercritical fluid gasification technology, as an environmentally friendly technology, can convert organic components of plastic waste into fuels and chemical materials. Moreover, the utilization of CO2 as the gasification environment holds significant importance for reducing carbon emissions. To better comprehend the microscopic mechanism of plastic gasification in supercritical environment, this sthdy used the Reactive Force Field (ReaxFF) molecular dynamics method to study the gasification process of long-chain poly(vinyl alcohol) molecule in supercritical H2O/CO2 under different reaction conditions. The result illustrated that during the gasification process, poly(vinyl alcohol) initially depolymerized into multiple long carbon chain (C5+) molecular fragments. Subsequently, these fragments underwent cleavage into short carbon chains and various gaseous small molecules. In this reaction, O radicals generated by CO2 decomposition play a crucial role in promoting the cleavage of plastic C–C bonds. In addition, through the analysis of the products and chemical bonds, we found that increasing temperature and prolonging reaction time significantly enhance the gasification efficiency and hydrogen production of plastics. Conversely, exceedingly high pressure inhibits the gasification reaction.

Mechanistic understanding of dehydroxylation reaction of smectites: Insights from reactive force field (ReaxFF) molecular dynamics simulation

Mechanistic understanding of dehydroxylation reaction of smectites: Insights from reactive force field (ReaxFF) molecular dynamics simulation

Atomic-level insight into the carburization process of iron-based catalysts: A ReaxFF molecular dynamics study

Transition metal carbide catalysts have garnered widespread attention due to their outstanding catalytic performance. The carbide catalysts, such as FexC and MoxC are typically obtained from their oxide carburization. The reduction and carburization processes are key steps during the activation of oxide precursors, which determine the activity and stability. An understanding of the carburization process mechanism is very important for the optimization of carbide catalysts. Iron-based catalysts are widely used in the large-scale coal-to-liquid industry because of their low price and high activity. In this paper, the carburization process of iron oxide nanoparticles was simulated by the Reactive force field (ReaxFF) molecular dynamics method. The results illustrate that the competition between CO dissociation and reduction of oxides occurs at the 100 ps time scale, which can be tuned by particle size and oxygen vacancy. We have explained the counter-intuitive finding that small oxide particles are more difficult to achieve fully carburization than larger ones; this is because rapid carbon accumulation on the surface blocks the oxygen diffusion channels from bulk to surface. The atomic distribution heat map was carried out to demonstrate the carbon and oxygen penetration processes. Meanwhile, the volumetric strain analysis reveals the driving force comes from the strong tendency to form Fe-C bonds. The dependence on surface orientation was further systematically investigated. This work provides microscopic insights into the carburization process of iron-based materials and the fundamental knowledge for the optimization of catalyst synthesis procedures.

High Temperature Induced Low Friction and Wear in a-C:Si via Formation of a "H Passivation Layer/a-SiO2/H Passivation Layer" Structure in a Humid Environment.

Doping Si into amorphous carbon can decrease humidity sensitivity, improve thermal stability, and retain excellent friction performance. Experimental studies have shown that Si-doped amorphous carbon formed Si-OH structures and frictional oxides in high-temperature and humid environments. However, the formation process of Si-OH and frictional oxides, as well as their structure, formation conditions, and antifriction properties, remains unclear. In this paper, reactive force field molecular dynamics (ReaxFF MD) was used to investigate the frictional performance of a-C and a-C:Si (7.2 atom %) at temperatures of 300, 700, and 1500 K in H2O environments. The results showed that with increasing temperature, the friction force of a-C increases from 8.2 nN at 300 K to 15.51 nN at 1500 K, while that of a-C:Si decreases from 10.3 nN at 300 K to 5.6 nN at 1500 K. In H2O environments, a-C:Si formed a "H passivation layer/a-SiO2/H passivation layer" structure, which inhibited the formation of interfacial bonds between the upper and lower substrates and reduced the wear of the substrate while ensuring the antifriction and antiwear properties of a-SiO2. This paper reveals the mechanism behind the low friction characteristics of a-C:Si in high-temperature and humid environments, providing theoretical guidance for the application of a-C:Si under such conditions.

Investigation on the thermal runaway mechanism of electrolyte in lithium-ion batteries via ReaxFF molecular dynamics

Lithium-ion batteries have the advantages of high energy density and high cycle times, and have been widely used in portable electronic devices, electric vehicles, and large-scale energy storage. However, lithium-ion batteries are prone to thermal runaway. Subsequently, electrolyte decomposition and combustion occur, leading to an increase in battery temperature and even causing fires or explosions. In order to explore the reaction mechanism of thermal runaway in lithium-ion battery electrolytes, the volatile and combustible organic solvents are selected as the research object. Three different organic solvents were established, namely pure ethylene carbonate (C3H4O3) solvent and its mixture with dimethyl carbonate (C3H6O3) and diethyl carbonate (C5H10O3), respectively. The effect of heating on the thermal runaway of organic solvents was studied using reactive force field molecular dynamics (ReaxFF MD). All three organic solvents will produce a large amount of CH2 free groups and flammable organic substances such as C2H4 during pyrolysis, which is the main reason for thermal runaway of lithium-ion batteries. The research results may contribute to preventing and suppressing thermal runaway in lithium-ion batteries.