Density Functional Molecular Dynamics Research Articles

Effect of water on formic acid and formaldehyde decomposition on the TiO2 (110) surface

The catalytic and photocatalytic performance of TiO2 in air pollutant degradation is significantly influenced by the adsorption of water. Here, we explore the molecular mechanism of formic acid and formaldehyde decomposition and their interaction with water on the TiO2 (110) surface, employing density functional theory (DFT) calculations and reactive molecular dynamics (RMD) simulations. RMD simulations indicate that due to the competitive adsorption of water at the surface Ti site, formic acid predominantly exists in a monodentate dissociative adsorption form on the TiO2 (110) surface. Moreover, on the TiO2 (110) surface, water molecules inhibit the adsorption and dissociation of formic acid, but they facilitate that of formaldehyde, forming methanediol (*CH2OHO) and dioxymethylene (*CH2O2). DFT calculations suggest that the formation pathway of *CH2OHO or *CH2O2 is energetically favorable, but the formation of formate is difficult. This contrasts with the adsorption of formaldehyde on the anatase surface, where formate species are formed.

Highly Reversible Sodium‐ion Storage in A Bifunctional Nanoreactor Based on Single‐atom Mn Supported on N‐doped Carbon over MoS2 Nanosheets

Conversion‐type electrode materials have gained massive research attention in sodium‐ion batteries (SIBs), but their limited reversibility hampers practical use. Herein, we report a bifunctional nanoreactor to boost highly reversible sodium‐ion storage, wherein a record‐high reversible degree of 85.65% is achieved for MoS2 anodes. Composed of nitrogen‐doped carbon‐supported single atom Mn (NC‐SAMn), this bifunctional nanoreactor concurrently confines active materials spatially and catalyzes reaction kinetics. In‐situ/ex‐situ characterizations including spectroscopy, microscopy, and electrochemistry, combined with theoretical simulations containing density functional theory and molecular dynamics, confirm that the NC‐SAMn nanoreactors facilitate the electron/ion transfer, promote the distribution and interconnection of discharging products (Na2S/Mo), and reduce the Na2S decomposition barrier.As a result, the nanoreactor‐promoted MoS2 anodes exhibit ultra‐stable cycling with a capacity retention of 99.86% after 200 cycles in the full cell. This work demonstrates the superiority of bifunctional nanoreactors with two‐dimensional confined and catalytic effects, providing a feasible approach to improve the reversibility for a wide range of conversion‐type electrode materials, thereby enhancing the application potential for long‐cycled SIBs.

Highly Reversible Sodium-ion Storage in A Bifunctional Nanoreactor Based on Single-atom Mn Supported on N-doped Carbon over MoS2 Nanosheets.

Conversion-type electrode materials have gained massive research attention in sodium-ion batteries (SIBs), but their limited reversibility hampers practical use. Herein, we report a bifunctional nanoreactor to boost highly reversible sodium-ion storage, wherein a record-high reversible degree of 85.65% is achieved for MoS2 anodes. Composed of nitrogen-doped carbon-supported single atom Mn (NC-SAMn), this bifunctional nanoreactor concurrently confines active materials spatially and catalyzes reaction kinetics. In-situ/ex-situ characterizations including spectroscopy, microscopy, and electrochemistry, combined with theoretical simulations containing density functional theory and molecular dynamics, confirm that the NC-SAMn nanoreactors facilitate the electron/ion transfer, promote the distribution and interconnection of discharging products (Na2S/Mo), and reduce the Na2S decomposition barrier.As a result, the nanoreactor-promoted MoS2 anodes exhibit ultra-stable cycling with a capacity retention of 99.86% after 200 cycles in the full cell. This work demonstrates the superiority of bifunctional nanoreactors with two-dimensional confined and catalytic effects, providing a feasible approach to improve the reversibility for a wide range of conversion-type electrode materials, thereby enhancing the application potential for long-cycled SIBs.

Highly Reversible Sodium-ion Storage in A Bifunctional Nanoreactor Based on Single-atom Mn Supported on N-doped Carbon over MoS2 Nanosheets.

Conversion-type electrode materials have gained massive research attention in sodium-ion batteries (SIBs), but their limited reversibility hampers practical use. Herein, we report a bifunctional nanoreactor to boost highly reversible sodium-ion storage, wherein a record-high reversible degree of 85.65% is achieved for MoS2 anodes. Composed of nitrogen-doped carbon-supported single atom Mn (NC-SAMn), this bifunctional nanoreactor concurrently confines active materials spatially and catalyzes reaction kinetics. In-situ/ex-situ characterizations including spectroscopy, microscopy, and electrochemistry, combined with theoretical simulations containing density functional theory and molecular dynamics, confirm that the NC-SAMn nanoreactors facilitate the electron/ion transfer, promote the distribution and interconnection of discharging products (Na2S/Mo), and reduce the Na2S decomposition barrier.As a result, the nanoreactor-promoted MoS2 anodes exhibit ultra-stable cycling with a capacity retention of 99.86% after 200 cycles in the full cell. This work demonstrates the superiority of bifunctional nanoreactors with two-dimensional confined and catalytic effects, providing a feasible approach to improve the reversibility for a wide range of conversion-type electrode materials, thereby enhancing the application potential for long-cycled SIBs.

Zea mays bracts extract as an eco-friendly corrosion inhibitor for steel in HCl pickling solution: Experimental and simulation studies

Active phytochemicals with unique electron structures can adsorb on metal surfaces and effectively mitigate metal corrosion. Recently, plant extracts have garnered significant attention as green and renewable corrosion inhibitors. In this study, the abundant agricultural byproducts, namely Zea mays bracts, were used as the extract raw materials, and Zea mays bracts extract (ZMBE) was served as an eco-friendly corrosion inhibitor for mild steel (MS) in 1 M HCl pickling solution. The organic substances in ZMBE were analyzed via ultra-high performance liquid chromatography- quadrupole time-of-flight mass spectrometry (UPLC-QTFMS). The interaction between the active functional groups and MS was investigated using Fourier transform infrared (FT-IR) and ultraviolet–visible (UV–visible) spectroscopy and X-ray photoelectron spectroscopy (XPS). The corrosion inhibition behavior was scrutinized through potentiodynamic polarization (PDP) curves and electrochemical impedance spectroscopy (EIS). The results show that functional groups such as aromatic rings, double bonds, and hydroxyls successfully adsorb on the MS surface to form the protective films. ZMBE exhibits a mixed-type corrosion inhibition with a “geometric coverage” effect. The corrosion inhibition efficiency (η) increases with ZMBE concentration and solution temperature, the optimum η with 5.0 g·L−1 ZMBE at 318 K is 96.2 %. The adsorption of active ingredients follows the Langmuir and El-Awady isotherms. Density functional theory (DFT) and molecular dynamics (MD) simulations prove the synergistic effect of complex components in ZMBE and the corrosion inhibition mechanism. ZMBE is a promising acid pickling corrosion inhibitor with broad application prospects.

Mechanical and electronic behaviour of TMDC nanotubes and monolayers: molecular simulations

ABSTRACT Transition metal dichalcogenides (TMDCs) are among the most exciting materials in nano-size particles. In this study, MX2 (M = Mo and W; X = S, Se, and Te) nanotubes and monolayers were evaluated to show the structural, mechanical, and electronic properties. The results showed that the stability of MX2 monolayers changes similarly to nanotubes with the sequence of MS2 > MSe2 > MTe2 (M = Mo and W). Besides, MX2 nanotubes and monolayers are semiconductors, and the band gap energy increases with a similar sequence with stability properties. The structural stability and band gap energy of WX2 structures are more than MoX2 structures. Young's modulus of nanotubes was studied with density functional theory (DFT) and molecular dynamics (MD) simulations with Stillinger-Weber (SW) potential methods. The results are similar to the formation and band gap energy showing that Young's modulus of the MX2 structures is in order of MS2 > MSe2 > MTe2 (M = Mo and W) and WX2 > MoX2 (X = S, Se or Te). Structural defects in monolayers, which were M-vacancy (VM), X2-vacancy (VX2), M-X2-vacancy (VM-X2), and M-X4-vacancy (VM-X4), were studied and it showed that the mechanical properties could be decreased. However, the defects do not affect electronic properties.

Biodegradability assessment of HDPE-based biocomposites: Influence of starch and fiber composition

This research aims to analyze the biodegradation dynamics of a tertiary composite blend, including High-Density Polyethylene (HDPE), starch and linen fiber, and their combined effect on decay processes in authentic environmental settings. It investigates the relationship between fiber content and decomposition rates, details the biodegradation mechanisms, and evaluates the reactive profiles of the involved constituents. Decay kinetics and the biodegradation mechanism of three formulations: HDPE60S40, HDPE60S20F20, and HDPE60S30F10, representing composites with 60 % HDPE, complemented by 40 %, 20 % starch and 20 %, 10 % linen fiber, respectively, are examined. HDPE60S30F10 is noted for its superior biodegradation rates, showing a 1.2 % weight loss in soil and 9.89 % in marine conditions and an increased resistance to shearing forces, whereas HDPE60S40 recorded a weight loss of 0,63 % in soil and 2.59 % in seawater against 1,7 % and 6.64 % in soil and seawtaer, respectively recorded with HDPE60S20F20. Density Functional Theory (DFT) and Molecular Dynamics (MD) simulations complement these findings, presenting HDPE60S40 as the most rigid, HDPE60S20F20 as the most ductile with a bulk modulus of 13.34 GPa, and HDPE60S30F10 exhibiting the best shear resistance with a shear modulus of 12.48 GPa. Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FTIR) analyses confirm microbial involvement and significant surface erosion, particularly indicating particularly starch degradation. The results suggest that integrating linen fiber into the composites enhances biodegradation.

Biodegradability assessment of HDPE-based biocomposites: Influence of starch and fiber composition

This research aims to analyze the biodegradation dynamics of a tertiary composite blend, including High-Density Polyethylene (HDPE), starch and linen fiber, and their combined effect on decay processes in authentic environmental settings. It investigates the relationship between fiber content and decomposition rates, details the biodegradation mechanisms, and evaluates the reactive profiles of the involved constituents. Decay kinetics and the biodegradation mechanism of three formulations: HDPE60S40, HDPE60S20F20, and HDPE60S30F10, representing composites with 60% HDPE, complemented by 40%, 20% starch and 20%, 10% linen fiber, respectively, are examined. HDPE60S30F10 is noted for its superior biodegradation rates, showing a 1.2% weight loss in soil and 9.89% in marine conditions and an increased resistance to shearing forces, whereas HDPE60S40 recorded a weight loss of 0,63% in soil and 2.59% in seawater against 1,7% and 6.64% in soil and seawtaer, respectively recorded with HDPE60S20F20. Density Functional Theory (DFT) and Molecular Dynamics (MD) simulations complement these findings, presenting HDPE60S40 as the most rigid, HDPE60S20F20 as the most ductile with a bulk modulus of 13.34GPa, and HDPE60S30F10 exhibiting the best shear resistance with a shear modulus of 12.48GPa. Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FTIR) analyses confirm microbial involvement and significant surface erosion, particularly indicating particularly starch degradation. The results suggest that integrating linen fiber into the composites enhances biodegradation.

Coordination structures and stabilities of Am(III) adsorption complexes at kaolinite(0 0 1)-water interface

Understanding the structures and stabilities of actinide species is crucial for comprehending the sorption mechanisms at mineral–water interfaces. However, the relevant molecular-level fundamental aspects of actinide coordination chemistry at the mineral–water interface remain unclear. We herein conduct a systematic theoretical study of coordination structures and adsorption energies of Am3+ and Am(OH)2+ sorption complexes at the kaolinite(001)-water interface by integrating static density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations. Computational results show that stable outer- and inner-sphere adsorption complexes are respectively formed through hydrogen bonding and coordinate bonding with surface aluminol groups. The most stable inner-sphere species are predicted to be tridentate surface complexes with an eight-folded coordination structure in the first coordination sphere of Am(III). This work deepens the understanding of Am(III) adsorption and complexation behaviors at the mineral–water interface, providing essential insights for actinide migration in natural environments and nuclear waste disposal. The synergy between static DFT calculations for initial screening and AIMD simulations for comprehensive dynamic analysis in this work enhances the efficiency and accuracy of theoretical predictions for actinide environmental chemistry and can be helpful for the broader research fields of geochemistry and environmental science.

Application of Computer Calculation in the Study of Grain Boundary

A grain boundary (GB) is a structure of great concern in materials research, which affects the mechanical properties and electrical conductivity of materials, but the microscopic thermodynamic properties of GBs cannot be explained comprehensively. In this review, we demonstrate a variety of calculation methods for GBs: density functional theory (DFT) and molecular dynamics (MDs) aim to extract the thermodynamic and kinetic properties of GBs on the atomic scale, and machine learning accelerates DFT or improves the accuracy of MDs. These methods explain the microscopic properties of a GB from different perspectives and are combined by machine learning. It is hoped that this review can inspire new ideas and provide more practical applications of computer calculations in GB engineering.

Unveiling a New 2D Semiconductor: Biphenylene-Based InN.

The two-dimensional (2D) materials class earned a boost in 2021 with biphenylene synthesis, which is structurally formed by the fusion of four-, six-, and eight-membered carbon rings, usually named 4-6-8-biphenylene network (BPN). This research proposes a detailed study of electronic, structural, dynamic, and mechanical properties to demonstrate the potential of the novel biphenylene-like indium nitride (BPN-InN) via density functional theory and molecular dynamics simulations. The BPN-InN has a direct band gap energy transition of 2.02 eV, making it promising for optoelectronic applications. This structure exhibits maximum and minimum Young modulus of 22.716 and 22.063 N/m, Poisson ratio of 0.018 and -0.008, and Shear modulus of 11.448 and 10.860 N/m, respectively. To understand the BPN-InN behavior when subjected to mechanical deformations, biaxial and uniaxial strains in armchair and zigzag directions from -8 to 8% were applied, achieving a band gap energy modulation of 1.36 eV over tensile deformations. Our findings are expected to motivate both theorists and experimentalists to study and obtain these new 2D inorganic materials that exhibit promising semiconductor properties.

Reversible phase transformations between Pb nanocrystals and a viscous liquid-like phase.

Phase transformations have been a prominent topic of study for both fundamental and applied science. Solid-liquid reaction-induced phase transformations can be hard to characterize, and the transformation mechanisms are often not fully understood. Here, we report reversible phase transformations between a metal (Pb) nanocrystal and a viscous liquid-like phase unveiled by in situ liquid cell transmission electron microscopy. The reversible phase transformations are obtained by modulating the electron current density (between 1000 and 3000 electrons Å-2 s-1). The metal-organic viscous liquid-like phase exhibits short-range ordering with a preferred Pb-Pb distance of 0.5 nm. Assisted by density functional theory and molecular dynamics calculations, we show that the viscous liquid-like phase results from the reactions of Pb with the CH3O fragments from the triethylene glycol solution under electron beam irradiation. Such reversible phase transformations may find broad implementations.

Probing the interaction mechanism of choline chloride-based deep eutectic solvents with flavonoid and polyphenol systems

Choline chloride-based deep eutectic solvents (DES) have been demonstrated as promising green solvents for the extraction of flavonoids and polyphenols. This study investigates the interaction between six different hydrogen bond donors (HBD) choline chloride-based DES and three types of polyphenolic flavonoid substrates. Density functional theory (DFT) and molecular dynamics (MD) simulations suggest that Cl− dominates the interaction primarily through electrostatic forces. The extraction effect of alcohol DES on rutin was optimized obviously, and the maximum interaction could reach 737.6 kJ/mol. Acid DES has a better extraction effect on anthocyanins, with a maximum interaction of 376.4 kJ/mol. With the increase of the carbon chain of HBA and the increase of the number of functional groups, the interaction between DES and the active substance decreases. As HBD, ethanolamine with both hydroxyl and amino groups showed the best effect in the extraction process of DES, forming the maximum interaction energy of 1575.8 kJ/mol. Additionally, multivariate analysis is employed to establish the relationship between different variables and interaction energy. This study provides micro-theoretical support for the extraction of flavonoids and polyphenols.

Unraveling the corrosion inhibition behavior of prinivil drug on mild steel in 1M HCl corrosive solution: insights from density functional theory, molecular dynamics, and experimental approaches

Unraveling the corrosion inhibition behavior of prinivil drug on mild steel in 1M HCl corrosive solution: insights from density functional theory, molecular dynamics, and experimental approaches

X-functionalized molybdenene monolayers (X = O, F, Al, Si, Cl)

Molybdenene synthesized experimentally is the sole Dirac material with metallic properties so far [Sahu et al., Nat. Nanotechnol. 18, 1430 (2023)], exhibiting a wide array of unique and outstanding properties with potentially extensive applications. However, the free-standing molybdenene structure is not so stable, which highly limits its further exploitation. In this work, we employ density functional theory calculations and ab initio molecular dynamics simulations to investigate molybdenene monolayers functionalized with various elements (X = H, Li, Be, B, C, N, O, F, Na, Mg, Al, Si, P, S, Cl) at both basal surfaces, aiming at achieving the stable free-standing molybdenene derivatives. By evaluating the energetic, mechanical, dynamical, and thermodynamic properties, we confirm some stable monolayer structures of X-functionalized molybdenene (X = O, F, Al, Si, Cl), which are named as X-Molybdenene. Therefore, our findings stabilize the molybdenene via surface functionalization, which is crucial for future experimental validations and applications.

Density functional theory and molecular dynamics study on the growth of graphene by chemical vapor deposition on copper substrate

Chemical vapor deposition is an affordable method for producing high-quality graphene. Microscopic defects in graphene grown on copper substrates, such as five- and seven-membered rings, degrade the quality of graphene. Therefore, it is essential to study the growth process and factors affecting the quality of graphene on copper surfaces. In this study, first-principles calculations based on density functional theory show that the four-step dehydrogenation reaction of methane is endothermic, with the energy barrier for the last dehydrogenation step being relatively high. Additionally, CH forms dimers on the copper surface with a lower energy barrier and trimers with a higher energy barrier, indicating that carbon dimers are the primary precursor species for graphene growth in the early stages. Subsequently, in molecular dynamics simulations, the analytical bond-order potential based on quantum mechanics is employed. The results reveal that the growth of graphene on the copper surface involves the diffusion and gradual nucleation of carbon dimers in the early stages, the gradual enlargement of graphene domains in the intermediate stages, and the gradual merging of graphene domain boundaries in the later stages. Moreover, the growth of graphene on the copper substrate follows a self-limiting growth mode. Increasing the deposition interval of carbon atoms and reducing the carbon atom deposition velocity contribute to enhancing the quality of graphene grown on the copper substrate.

Carborane-Cluster-Wrapped Copper Cluster with Cyclodextrin-like Cavities for Chiral Recognition.

Chiral atomically precise metal clusters, known for their remarkable chiroptical properties, hold great potential for applications in chirality recognition. However, advancements in this field have been constrained by the limited exploration of host-guest chemistry, involving metal clusters. This study reports the synthesis of a chiral Cu16(C2B10H10S2)8 (denoted as Cu16@CB8, where C2B10H12S2H2 = 9,12-(HS)2-1,2-closo-carborane) cluster by an achiral carboranylthiolate ligand. The chiral R-/S-Cu16@CB8 cluster features chiral cavities reminiscent of cyclodextrins, which are surrounded by carborane clusters, yet they crystallize in a racemate. These cyclodextrin-like cavities demonstrated the specific recognition of amino acids, as indicated by the responsive output of circular dichroism and circularly polarized luminescence signals of Cu16 moieties of the Cu16@CB8 cluster. Notably, a quantitative chiroptical analysis of amino acids in a short time and a concomitant deracemization of Cu16@CB8 were achieved. Density functional tight-binding molecular dynamics simulation and noncovalent interaction analysis further unraveled the great importance of the cavities and binding sites for chiral recognition. Dipeptide, tripeptide, and polypeptide containing the corresponding amino acids (Cys, Arg, or His residues) display the same chiral recognition, showing the generality of this approach. The functional synergy of dual clusters, comprising carborane and metal clusters, is for the first time demonstrated in the Cu16@CB8 cluster, resulting in the valuable quantification of the enantiomeric excess (ee) value of amino acids. This work opens a new avenue for chirality sensors based on chiral metal clusters with unique chiroptical properties and inspires the development of carborane clusters in host-guest chemistry.

Amelioration of protective organic layer using acenaphthene-based inhibitor responsible for excellent anti-corrosion performance: Experimental and computational perspectives

Despite the engineering promise offered by the co-existence of organic substances in protecting vulnerable metallic materials from corrosive environments, the interaction and formation mechanisms that induce the development of new materials with improved structural properties remain less understood. This study investigated the corrosion inhibitory properties of two acenaphthene derivatives, acenaphthylene-1,2‑dione (ACP) and 1,2-dihydroacenaphthylen-1-ol (DCP), as inhibitors for N80 steel in a 15 % HCl solution. The anticorrosive effectiveness of ACP and DCP compounds was evaluated through multiple research methods, including weight loss analysis, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and surface characterization using scanning electron microscopy (SEM). The experimental findings demonstrate that ACP exhibits superior inhibition performance compared to DCP, with an inhibition efficiency of 93.54 % for ACP and 73.12 % for DCP at an optimum concentration of 5 × 10–3 M. EIS data show that the charge transfer resistance increases with higher concentrations of both compounds. PDP results indicate that ACP and DCP act as mixed-type inhibitors without altering the corrosion mechanism. The kinetic parameters of corrosion adsorption follow the Langmuir isotherm, highlighting a competition between physical and chemical interactions. To investigate how the geometric structures resulting from functional groups influence their interaction with the metal surface, theoretical calculations employing density functional theory (DFT), molecular dynamics (MD), and density-functional tight-binding (DFTB) were conducted. These calculations were aimed at gaining insights into the adsorption behavior of ACP and DCP on the metal surface and their interfacial mechanism. The calculations demonstrate that the molecule possessing twin donor atoms along with p-type orbitals of aromatic rings significantly influenced the formation of a protective film with a uniform distribution. This configuration exhibited superior corrosion performance compared to a molecule containing only one hydroxyl group (—OH). Theoretical calculations further suggest that ACP exhibits stronger adsorption ability, with the two oxygen atoms identified as the most reactive sites, indicating their tendency to donate electrons to the iron surface. The robust resonance-stabilized structure of ACP enhances the stability of the molecules, facilitating its interaction and adsorption onto the metal surface compared to the DCP inhibitor. Overall, the superior inhibition performance of ACP is attributed to the close bonding of twin donor fragments within the ACP molecule, forming a more compact adsorbed inhibitor film on the steel surface.

Formation of Supernarrow Borophene Nanoribbons

AbstractBorophenes have sparked considerable interest owing to their fascinating physical characteristics and diverse polymorphism. However, borophene nanoribbons (BNRs) with widths less than 2 nm have not been achieved. Herein, we report the experimental realization of supernarrow BNRs. Combining scanning tunneling microscopy imaging with density functional theory modeling and ab initio molecular dynamics simulations, we demonstrate that, under the applied growth conditions, boron atoms can penetrate the outermost layer of Au(111) and form BNRs composed of a pair of zigzag (2,2) boron rows. The BNRs have a width self‐contained to ∼1 nm and dipoles at the edges to keep them separated. They are embedded in the outermost Au layer and shielded on top by the evacuated Au atoms, free of the need for post‐passivation. Scanning tunneling spectroscopy reveals distinct edge states, primarily attributed to the localized spin at the BNRs’ zigzag edges. This work adds a new member to the boron material family and introduces a new physical feature to borophenes.

Formation of Supernarrow Borophene Nanoribbons.

Borophenes have sparked considerable interest owing to their fascinating physical characteristics and diverse polymorphism. However, borophene nanoribbons (BNRs) with widths less than 2 nm have not been achieved. Herein, we report the experimental realization of supernarrow BNRs. Combining scanning tunneling microscopy imaging with density functional theory modeling and ab initio molecular dynamics simulations, we demonstrate that, under the applied growth conditions, boron atoms can penetrate the outermost layer of Au(111) and form BNRs composed of a pair of zigzag (2,2) boron rows. The BNRs have a width self-contained to ∼1 nm and dipoles at the edges to keep them separated. They are embedded in the outermost Au layer and shielded on top by the evacuated Au atoms, free of the need for post-passivation. Scanning tunneling spectroscopy reveals distinct edge states, primarily attributed to the localized spin at the BNRs' zigzag edges. This work adds a new member to the boron material family and introduces a new physical feature to borophenes.