Ab Initio Molecular Dynamics Study Research Articles

Synergistic Improvement of Antibacterial and Osteogenic Differentiation of Thermomechanically Processed Mg-Zr-Sr-Ce Alloy: Insights into the Role of Precipitate Evolution Supported by AIMD Simulation Study.

In the present study, we have discussed the influence of forging temperature (623 K (FT623), 723 K (FT723) and 823 K (FT823)) on microstructure and texture evolution and its implication on mechanical behavior, in vitro-in vivo biocorrosion, antibacterial response, and cytocompatibility of microalloyed Mg-Zr-Sr-Ce alloy. Phase analysis, SEM, and TEM characterization confirm the presence of Mg12Ce precipitate, and its stability was further validated by performing ab initio molecular dynamic simulation study. FT723 exhibits strengthened basal texture, higher fraction of second phases, and particle-stimulated nucleation-assisted DRX grains compared to other two specimens, resulting in superior strength with comparable ductility. FT723 also exhibits superior corrosion resistance mainly due to the strengthened basal texture and lower dislocation density. All the specimens exhibit excellent antibacterial behavior with Gram-negative E. coli, Gram-positive Staphylococcus aureus, and Pseudomonas aeruginosa bacteria. 100% reduction of bacterial growth is observed within 24 h of culture of the specimens. Cytocompatibility was determined by challenging specimen extracts with the MC3T3-E1 cell lines. FT723 specimen exhibits the highest cell proliferation and alkaline phosphatase activity (ALP) because of its superior corrosion resistance. The ability of the specimens to be used in orthopedic implant application was evaluated by in vivo study in rabbit femur. Neither tissue-related infection nor the detrimental effect surrounding the implant was confirmed from histological analysis. Significant higher bone regeneration surrounding the FT723 specimen was observed in SEM analysis and fluorochrome labeling. After 60 days, the FT723 specimen exhibits the highest bone formation, suggesting it is a suitable candidate for orthopedic implant application.

Ab initio molecular dynamics study on the local structures and solid/liquid interface in liquid Al-Ti and Al-B-Ti alloys

High-purity aluminum, owing to its excellent physical and chemical properties, finds extensive applications across various fields. A comprehensive understanding of the local structure of liquid Al-based alloys and the characteristics of solute atoms at the forefront of the solid-liquid interface is highly advantageous for the purification of aluminum. Ab initio molecular dynamics (AIMD) simulations were employed to study the local structures, element interactions and electronic structures in Al-Ti and Al-B-Ti melts, together with the behaviors of Ti atom and B-Ti atom pair at the solid/liquid interface forefront of Al. In the Al-B-Ti ternary melt, there are stronger interactions between B and Ti atoms than those between Al and B atoms as well as between Al and Ti atoms. The introduction of B atoms leads to the disruption of Al-Ti bonds and the formation of B-Ti bonds, thereby altering the state of Ti atoms in the melt and then influencing their diffusion properties. The dynamic process of B-Ti bond formation in the melt has been elucidated. The bond angle distribution function shows that the geometric configuration around Ti atoms in the Al melt undergoes significant changes with the addition of B atoms. A strong hybridization occurs between the 3d orbital of Ti atom and the 2p orbital of B atom. Moreover, a notable charge accumulation between B and Ti atoms, indicates the strong interaction between them. The addition of Ti atom can promote the migration of the Al solid/liquid interface. The B-Ti bond is very stable at the forefront of the Al solid/liquid interface, and the formation of B-Ti bond significantly drag the migration of the Al solid/liquid interface.

Ab initio molecular dynamics study of interactions between isolated polyhedral oligomeric silsesquioxane trisilanols and aluminum

Trisilanol polyhedral oligomeric silsesquioxane (POSS) are a category of inorganic–organic material that comprise an inorganic open cage silica structure, organic attachments, and silanol (SiOH) groups. Recently, trisilanol POSS was added to Al-based alloys, and found to promote substantial microstructural refinement, and improved mechanical strength and fatigue life compared to conventional compositions. Such microstructural modifications and property enhancements are usually attributed to silanolAl bonds that formed within the liquid-state, prior to solidification. However, details of such high-temperature chemical interactions remain unclear. Here, we performed ab initio molecular dynamics simulations at 1500 K, to probe the chemical interactions between isolated trisilanol POSS molecule and discreet Al atoms. Al atoms modified the silanol groups to form, two energetically favorable coordinate complexes: monodentate SiOAl and bidentate (SiO)2Al. Such complexes were formed by Al atoms attracting electrons towards themselves from the POSS molecule. Crucially, this bonding mechanism allowed trisilanol POSS to organize the neighboring Al atoms into geometric motifs that can potentially serve as nucleation sites within liquid-Al, and facilitate microstructural refinement.

β-D-Glucopyranose-silver+ (1:1) complex as a small gas molecule scavenger.

In this article, density functional theory computations at the PBE0-D3/def2-TZVP level are reported to unveil the type of bonding between β-D-glucopyranose-silver ion (1:1) complex ([Ag(C6H12O6)]+) and seven gas molecules, namely, H2, C2H2, C2H4, CO, N2, NO and O2. Moreover, the relative preference of trapping among these molecules within the sight of Ag metal ion in the complex is explored. The nature of interaction of these small molecules with the [Ag(C6H12O6)]+ ion is studied. Exergonic nature of binding is noted with the metal center for all the chosen small molecules except O2. Thermochemical data reveals the binding preference of C2H4 > C2H2 > CO > NO > N2 > H2. Natural bond orbital analysis, contour plot of the Laplacian of electron density, electron density descriptors, and gradient isosurface help in understanding the nature of interactions. Maximum bond formation is noted between the Ag-complex and CO molecule. Assessed energy decomposition analysis discloses the nature of interaction as mainly orbital between the bound small gas molecules and the Ag-complex. Frontier molecular orbital pictures further help in understanding the type of interaction as orbital. To disclose the kinetic stability of the gas molecule bound Ag complexes an ab initio molecular dynamics study is done at different temperatures up to 2 ps. These studies help in understanding the type of adsorption. Calculated conceptual density functional theory (CDFT) based reactivity descriptors corroborate well with results. β-D-glucopyranose-silver ion (1:1) complex may be used as small gas molecule scavenger.

Global minimum and a heap of low-lying isomers with planar tetracoordinate carbon in the CAl3MgH2- system.

A global minimum and a heap of low-lying isomers with planar tetracoordinate carbon (ptC) are identified in the CAl3MgH2- system by computational quantum chemical investigations. The nature of the chemical bonding in the global minimum ptC isomer is examined using the conceptual quantum chemical tools. The atoms in molecule (AIM) analysis reveals that the global minimum isomer possesses a ptC geometry. Additionally, the adaptive natural density partitioning (AdNDP), electron localization function (ELF), and nucleus-independent chemical shifts (NICS) analysis corroborate the presence of delocalization in the ptC isomer. The delocalization of electron density in the global minimum ptC isomer contributes to attaining structural stability. The results also suggest that the bridging hydrogen plays a crucial role in stabilizing the ptC system. Furthermore, the ab initio molecular dynamics study supports the structural stability of the ptC isomer.

Role of Copper as Current Collectors in the Reductive Reactivity of Polymers for Anode-Free Lithium Metal Batteries - Insights from DFT and AIMD Studies

Understanding the role of current collectors (CCs) in the reductive reactivity of polymers on Li metal and the resultant solid electrolyte interphase (SEI) formation is essential for improving the performance of anode-free lithium metal batteries (AFLMBs). In this study, we have examined the reactivity of three polymeric hosts: poly(ethylene oxide) (PEO), poly(ε-caprolactone) (PCL), and poly(trimethylene carbonate) (PTMC) at Li metal supported on Cu surfaces (Li/Cu) using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. In particular, the effect of copper (Cu) CCs on polymer stability, electronic structure, and their reduction reactions is investigated and compared to that of pure Li (100) surface. Through time-dependent Bader charge transfer analysis, electron transfer is identified as the triggering factor for polymer reduction. Based on the simulations, we find that the Cu CCs have a significant influence on the charge distribution of the Li metals, which increases electron transfer to the polymers and thereby accelerates polymers reduction. This thereby leads to different reaction mechanisms as compared to on Li-metal. The findings suggest that utilization of Cu CCs avoid production of CO molecules and improves the quality of the formed SEI layer. Figure 1

Theoretical Studies on the Isomerization Kinetics of Low-Lying Isomers of the SiC4H2 System.

The low-lying isomers of SiC4H2 are investigated to understand the kinetics of isomerization pathways using density functional theory. In our earlier work, we studied the various possible isomers (J. Phys. Chem. A, 2020, 124, 987-1002) and the chemical bonding of low-lying isomers of SiC4H2 (J. Phys. Chem. A, 2022, 126, 9366-9374). Among them, four isomers, 1-ethynyl-3-silacycloprop-1-en-3-ylidene (1), 3-silapent-1,4-diyn-3-ylidene (2), 1-silapent-1,2,3,4-tetraen-1-ylidene (4), and 1-silapent-2,4-diyn-1-ylidene (5) have already been identified in the laboratory. The previously known theoretical isomer 2-methylene-1-silabicyclo[1.1.0]but-1(3)-en-4-ylidene (3) and the newly identified unknown isomer through the present kinetic studies 5-silabicyclo[2.1.0]pent-1(4),2-dien-5-ylidene (N6) remain elusive in the laboratory to date. The isomerization pathways of the low-lying isomers of SiC4H2 are predicted through the transition state structures. Intrinsic reaction coordinate analysis identifies the minimum energy reaction pathways connecting the transition state from one isomer to another of the investigated system. The present kinetic data reveal the isomerization of global minimum energy isomer 1 to thermodynamically stable low-lying isomers, 2 and 5. Interestingly, isomer 3 interconverts to the experimentally known low-energy isomer 4, the second most thermodynamically stable isomer among them. The thermodynamic and kinetic parameters of the low-lying isomers of SiC4H2 are also documented in this work. The rate coefficient and equilibrium constant for isomerization reactions are calculated using the Rice-Ramsperger-Kassel-Marcus theory. The equilibrium constant delineates the difficulties in forming N6 and 3 through the isomerization pathways. Furthermore, ab initio molecular dynamics studies dictate the stability of low-lying isomers of SiC4H2 within the time scale of the simulation.

Ab initio molecular dynamics study of the local structures and migration behaviors of liquid Sb-based alloys

High-purity Sb is widely applied in the semiconductor industry, infrared detection and non-volatile memory. An in-depth knowledge of the local structure and related properties in liquid Sb-based alloys proves to be highly advantageous in the purification of Sb. In this work, an ab initio molecular dynamics simulation was used to study the local structures, dynamical properties, electronic structures and migration behaviors of liquid X-containing (X = As, Bi, Cu, Fe) Sb-based alloys. Among these solute atoms, the distribution coefficient of As/Bi is much larger than that of Cu/Fe. The results showed that the local structures around As/Bi are looser than those around Cu/Fe. The local structure around As/Bi contains a higher fraction of low-index bond pairs than that around Cu/Fe, and its local topological order of triples is closer to pure Sb melt. The coordination polyhedrons using As/Bi as the centered atom have more relaxed short-range order clusters than those using Cu/Fe as the centered atom. Different local structures and chemical effects may lead to different migration behaviors of solute atoms in the Sb melt.

Effect of electronegative atoms on [formula omitted] – [formula omitted] stacking and hydrogen bonding behavior in simple aromatic molecules — An Ab initio MD study

Ab initio molecular dynamics studies have been performed on fluorobenzene, phenol, and aniline, which have the three most electronegative atoms, fluorine, oxygen, and nitrogen, respectively. Radial distribution functions show strong hydrogen bonding in the phenolic –OH group, whereas it is less prominent in the –NH2 group of aniline. Fluorobenzene does not show strong hydrogen bonds as no solvation shell is found between the fluorine atom and different aromatic hydrogens of the molecule. Spatial distribution functions show that the nitrogen atom of aniline interacts with the aromatic plane, the oxygen atom of phenol is concentrated near the –OH group and fluorobenzene’s fluorine atom interacts with the para hydrogen. Liquid phase dimer structures of these systems reveal that perpendicular orientation (Y-shaped) is preferred over parallel ones. Almost half of the total dimer population tends to prefer 90∘±30° angle. H-bond analyses show that fluorobenzene has the longest mean H-bond lifetime for the H-bond between the aromatic hydrogens and the fluorine atoms, whereas the aniline has the least. The mean lifetime between aromatic hydrogens and electronegative atoms increases steadily from aniline to fluorobenzene. Phenolic –OH and amino –NH2 groups show considerably longer mean H-bond lifetime than the aromatic hydrogens. Gas-phase binding energies obtained from quantum chemical calculations show that aniline and phenol dimers have higher binding energy values than the fluorobenzene dimer. Only the phenol dimer shows a perpendicular structure as a stable one, while aniline and fluorobenzene prefer the parallel orientation.

Ethane and Propane Dehydrogenation on Small Platinum Clusters Supported on Silica: An Ab Initio Molecular Dynamics and DFT Study.

The size-dependent activity of catalysts has been researched for a long time in the field of catalysis. Positively charged small Pt clusters enhance catalytic activity than bigger clusters and bulk for propane dehydrogenation. We performed DFT calculations on small Pt clusters adsorbed on silica support. The planar structure of Pt clusters is present till 4 Pt atoms, after which three-dimensional structures are observed. AIMD and DFT calculations for silica showed that it has a high surface area and thermal stability suitable to conduct dehydrogenation reactions. The adsorption of Pt cluster on silica results in the formation of directional bonds which affects the properties of the adsorbed Pt catalysts by changing the redox properties. In the bulk phase, ethane and propane molecules undergo dehydrogenation reactions with 0.133 eV atom-1 and 0.244 eV atom-1 energies, respectively. NEB calculations showed that except for Pt-2/SiO2 , all the even Pt clusters require less activation energy than the neighboring odd Pt clusters. Ethane molecule interacting with Pt-4/SiO2 , Pt-5/SiO2 , Pt-6/SiO2 , and propane with Pt-3/SiO2, Pt-4/SiO2 , Pt-5/SiO2 , Pt-6/SiO2 , follows the reverse Horiuti-Polanyi mechanism during dehydrogenation, whereas non-reverse Horiuti-Polanyi mechanism (which requires comparatively lower activation energy) is followed for smaller Pt clusters.

Ab initio molecular dynamics study of intersystem crossing dynamics for MH2 (M = Si, Ge, Sn, Pb) on spin-pure and spin-mixed potential energy surfaces.

Recently, surface-hopping ab initio molecular dynamics (SH-AIMD) simulations have come to be used to discuss the mechanisms and dynamics of excited-state chemical reactions, including internal conversion and intersystem crossing. In dynamics simulations involving intersystem crossing, there are two potential energy surfaces (PESs) governing the motion of nuclei: PES in a spin-pure state and PES in a spin-mixed state. The former gives wrong results for molecular systems with large spin-orbit coupling (SOC), while the latter requires a potential gradient that includes a change in SOC at each point, making the computational cost very high. In this study, we systematically investigate the extent to which the magnitude of SOC affects the results of the spin-pure state-based dynamics simulations for the hydride MH2 (M = Si, Ge, Sn, Pb) by performing SH-AIMD simulations based on spin-pure and spin-mixed states. It is clearly shown that spin-mixed state PESs are indispensable for the dynamics simulation of intersystem crossing in systems containing elements Sn and Pb from the fifth period onward. Furthermore, in addition to the widely used Tully's fewest switches (TFS) algorithm, the Zhu-Nakamura (ZN) global switching algorithm, which is computationally less expensive, is applied to SH for comparison. The results from TFS- and ZN-SH-AIMD methods are in qualitative agreement, suggesting that the less expensive ZN-SH-AIMD can be successfully utilized to investigate the dynamics of photochemical reactions based on quantum chemical calculations.

Unveiling the dynamic thermal separation process of CO2 on the surface of calcium oxide: An ab-initio molecular dynamics study with experimental verification

Heating to release CO2 captured by Calcium oxide is one of the crucial steps in CO2 capture technology. However, the molecular mechanism underlying CO2 thermal desorption and the impact of CaO hydration on CO2 desorption remain unclear. Based on ab initio molecular dynamics (AIMD), a comprehensive analysis of the desorption and regeneration mechanism of carbonized CaO surfaces was conducted. Temperature is the primary factor responsible for CO2 thermal desorption on CaO surfaces. Simulations of CO2 thermal-dynamic desorption indicate that the desorption temperature range of CO2 from a dry CaO surface was between 400 and 500 °C. The explicit solvent model was utilised to simulate the desorption of CO2 under hydration condition. In the temperature range of 25–800 °C, the desorption behaviour of CO2 is substantially inhibited in the presence of water layers and Ca(OH)2. Consistent with the AIMD results, the thermal desorption experiment following CO2 adsorption confirmed that the desorption temperature of CO2 increases considerably when the adsorbed sample hydrates. Consequently, the desorption process of CO2 on CaO surface was comprehensively elucidated by a combination of theoretical study and experimental validation, thereby guiding the development and regeneration of CaO-based adsorbents.

AIMD study and experimental verification of Ge-doped Fe80P13C7 amorphous soft magnetic alloys

Fe80P13-xC7Gex (x = 0, 2, 4) amorphous alloys were synthesized by rapid solidification technique and studied using Ab-initio molecular dynamics (AIMD) and first-principles calculations based on density-functional theory (DFT) for their electronic structures. Brillouin function was used to calculate saturation magnetization (µ0MS) at elevated temperatures utilizing experimentally measured Curie temperature (TC) and µ0MS at 0 K calculated by DFT.To verify the calculated µ0MS, ingots of Fe80P13-xC7Gex (x = 0, 1, 2, 3, 4, 5, 6) alloy were prepared by melt-spinning. An increase in experimental µ0MS with Ge concentration agrees with the calculated µ0MS. TC also increases with Ge concentration. Partial substitution of Ge for P enhances the µ0MS to 1.63 T (x = 4) from 1.46 T (x = 0), which indicated that the Fe80P13-xC7Gex (x = 4) shows optimum soft magnetic properties.

Non-covalent interactions between dihydroquercetin and arabinogalactan molecules: Theoretical study

Non-covalent interactions between Dihydroquercetin (or Taxifolin) (DHQ) and Arabinogalactan (AG) were systematically studied by using a set of theoretical techniques. Symmetry-adapted perturbation theory (SAPT0) calculations confirmed that dispersion and electrostatic interactions play the main role in attractive interactions of the DHQ/AG system (either contributes ∼40%), whereas induction forces contribute into the interaction energy (Eint) only moderately (∼15%). Independent gradient model (IGM) analysis explicitly showed existence of non-covalent interactions, including hydrogen bonds (H-bonds) in the DHQ/AG complex. Ab initio molecular dynamics studies indicated stability of DHQ/AG at room temperature. Finally, we established a stabilization of the DHQ/AG complex in solvents. Our investigations unveil the physical aspects of non-covalent interactions exist in the complex studied of two biomolecules.

Role of copper as current collectors in the reductive reactivity of polymers for anode-free lithium metal batteries - Insights from DFT and AIMD studies

Understanding the role of current collectors (CCs) in the reductive reactivity of polymers on Li metal and the resultant solid electrolyte interphase (SEI) formation is essential for improving the performance of anode-free lithium metal batteries (AFLMBs). In this study, we have examined the reactivity of three polymeric hosts: poly(ethylene oxide) (PEO), poly(ε-caprolactone) (PCL), and poly(trimethylene carbonate) (PTMC) at Li metal supported on Cu surfaces (Li/Cu) using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. In particular, the effect of copper (Cu) CCs on polymer stability, electronic structure, and their reduction reactions is investigated and compared to that of pure Li (100) surface. Through time-dependent Bader charge transfer analysis, electron transfer is identified as the triggering factor for polymer reduction. Based on the simulations, we find that the Cu CCs have a significant influence on the charge distribution of the Li metals, which increases electron transfer to the polymers and thereby accelerates polymers reduction. This thereby leads to different reaction mechanisms as compared to on Li-metal. The findings suggest that utilization of Cu CCs avoids the production of CO molecules and improves the quality of the formed SEI layer.

Ab Initio Molecular Dynamics Study of the Proton Transfer in Hydroxyl Ion-Induced Hydrolysis of Aluminum Monomers.

The hydrolysis process of Al(H2O)63+ induced by hydroxyl ions (OH-) is significant to aluminum solution chemistry. Previous investigations of hydrolysis reactions have primarily relied on static calculations in an implicit solvent environment. Herein, we employ ab initio molecular dynamics (AIMD) to investigate the evolution process of Al(H2O)63+ under various local alkaline conditions in an explicit solvent environment. Our work demonstrates the effect of solvent water in hydrolysis reactions. Specifically, the stepwise hydrolysis reaction induced by hydroxyl ions involves water wire compression and concerted proton transfers. Dehydration reactions occur when the number of hydroxyl ligands attached to the aluminum ion (Al3+) equals or exceeds three. Moreover, the Al(H2O)n(OH)3 species exhibit unique hydrolysis and dehydration reaction characteristics compared to other species. The geometrically stable aluminum monomers determined by AIMD are Al(H2O)5(OH)12+, Al(H2O)4(OH)2+, Al(H2O)1(OH)3, and Al(OH)4-. In addition, the topological analysis analyzes the interaction between Al3+ and coordinated H2O in different configurations, indicating the weakest interaction appearing in Al(H2O)n(OH)3 species.

Ab initio molecular dynamics study of H2 dissociation mechanisms on Cu13 and defective graphene-supported Cu13 clusters: active sites, energy barriers and adsorption states.

Ab initio molecular dynamics calculations were performed to study H2 dissociation mechanisms on Cu13 and defective graphene-supported Cu13 clusters. The study reveals that seven types of corresponding dissociation processes are found on the two clusters. The average dissociation energy barriers are 0.51 eV on the Cu13 cluster and 0.12 eV on the defective graphene-supported Cu13 cluster, which are lowered by ~ 19% and ~ 81% compared with the pristine Cu(111) surface, respectively. Furthermore, compared with the pure Cu13 cluster, the average dissociation energy barrier on the defective graphene-supported Cu13 cluster is substantially reduced by about 76%. The preferred dissociation mechanisms on the two clusters are H2 located at a top-bridge site with the barrier heights of 0.30 eV on the Cu13 cluster and - 0.31 eV on the defective graphene-supported Cu13 cluster. Analysis of the H-Cu bond interactions in the transition states shows that the antibonding-orbital center shifts upwards on the defective graphene-supported Cu13 cluster compared with the one on the Cu13 cluster, which explains the reduction of the dissociation energy barrier. The average adsorption energy of dissociated H atoms is also greatly enhanced on the defective graphene-supported Cu13 cluster, about twice that on pure Cu13.

Two Layers of Computational Screening on Silaborane‐based Clusters Filter Ca(SiB11H11CH3)2 as the Promising Electrolyte for Calcium‐Ion Batteries

AbstractCalcium‐ion batteries (CIBs) are promising energy storage systems, but the unavailability of adept electrolytes has hindered their development. In this work, a range of silaborane clusters ( ; n=5–15) were investigated using density functional theory (DFT) at ωB97XD3/6‐311+G(d,p) level of theory. The vertical detachment energy (VDE), electrochemical stability window (ESW) and binding energy (BE) of the silaboranes were computed at the same level of DFT. A methodology based on molecular electrostatic potential surface analysis was designed to locate the most suitable binding site for calcium ions on the clusters. DFT results show that the SiB11 cluster turns out to be superior to other candidates. Effect of substitution on silaboranes ( R− R=−CH3, −NCS, −CF3, −F and −Cl) was computed. −NCS and −CF3 substituted SiB11 ions were found to be the best from DFT. Ab initio molecular dynamics (AIMD) studies were performed to explore the interactions between silaborane‐based electrolytes and the Ca anode. AIMD results highlight the decomposition of −NCS and −CF3 substituted SiB11 on Ca anode. DFT and AIMD studies reveal that −CH3 substituted silaborane‐based Ca‐salt (Ca(SiB11H11CH3)2) is the promising electrolyte for CIBs.

Investigating Chlorination and Migration Mechanism of NaCl on C−S−H: DFT and AIMD Study**

AbstractThe present study investigates the chlorination and migration mechanism of Tobermorite9 Å through the use of density functional theory (DFT) calculation and ab initio molecular dynamics (AIMD). The findings reveal a negative adsorption energy value of −2.19488 eV. The results of the charge density difference analysis reveal that the Ca atoms experience electron loss, while the Cl atom undergoes electron gain. The O atom situated at the end of the silicate chain (and silicate chain bridge) exhibits electron gain, and the Na atom experiences electron loss. The results of density of states (DOS) and partial density of states (PDOS) demonstrate that the Ca−Cl bond was created as a result of the interaction between Ca and Cl orbitals. The evident overlaps between Na‐p and O24‐p orbitals lead to the formation of Na−O bond. In AIMD simulation, the minimum energy barrier and activation energy of sodium chloride molecule are 0.09236 eV and 0.059 eV, respectively. The findings also suggest that chloride ion diffusion is facile on hydrated calcium silicate.

Monitoring the Micro-Structural Evolution Mechanism of Next-Generation Ultra-High-Energy All-Nitrogen Materials: A Molecular Dynamic Study

Micro-structural evolution mechanisms of next-generation ultra-high-energy all-nitrogen materials under the extreme conditions of high temperature coupled with high pressure were revealed by state-of-the-art ab initio molecular dynamics studies based on highest-nitrogen-content energetic material 2,2'-azobis(5-azidotetrazole). The results indicate that there are three primary initial uni-molecular decomposition pathways, namely, tetrazole ring opening, azido group elimination, and the breaking of the N-N bond between the azo group and azidotetrazole. In complicated global decomposition reactions, there exists the formation of nitrogen-rich clusters and all-nitrogen species. Lowering the temperature or increasing the pressure is conducive to increasing the N content in the nitrogen-rich cluster and widening the time distribution for the cluster. Abundant all-nitrogen species N4, N5, N6, N7, N8, N9, N10, and N13 were formed, and their detailed evolutionary process and construction mechanisms were enunciated. We innovatively constructed a series of next-generation ultra-high-energy all-nitrogen materials, which are expected to realize the controllable construction of next-generation ultra-high-energy all-nitrogen materials under extreme conditions.