Search Results (246)

Molten salt chlorination is a key industrial route for producing titanium tetrachloride (TiCl₄), yet the atomistic catalytic role of iron (Fe) in the carbothermic chlorination of titanium oxides remains unclear. Here, the chlorination behavior of the NaCl–C–Cl₂–FeTiO₃ system was investigated by combining thermodynamic calculations with Ab Initio Molecular Dynamics (AIMD) and Deep Potential Molecular Dynamics (DPMD) simulations. AIMD results show that carbon adjacent to Fe exhibits enhanced reactivity, and that Fe-C synergistic electron transfer promotes both titanium oxide reduction and subsequent titanium chlorination. DPMD results further reveal that Fe not only accelerates these transformations, but also improves interfacial contact among carbon, titanium oxides, and molten salt, thereby enhancing mass transfer and shortening the formation time of TiCl₄. Temperature-dependent analysis indicates that Fe-C and C-O coordination numbers remain high near 1073 K, where TiCl₄ formation is efficient and relatively stable. Although increasing temperature can further enhance diffusion, its effect on reaction acceleration is limited, while excessively high temperatures weaken Fe-C interactions and reduce catalytic efficiency. These findings clarify the catalytic mechanism of Fe in molten salt chlorination at the atomic scale and provide theoretical support for process optimization. Full article

Molecular dynamics simulations were performed on 27 deep eutectic solvents (DESs) composed of various hydrogen bond acceptors (HBAs)—tetrabutylammonium bromide (TBAB), tetrabutylammonium chloride (TBAC), and tetraethylammonium chloride (TEAC)—combined with different hydrogen bond donors (HBDs)—3-aminopropan-1-ol (AP), 2-(methyl-amino)ethanol (MAE), and 2-(n-butylamino)ethanol (BAE). Radial distribution functions (RDFs) were computed from the simulation trajectories to probe the microscopic structure of these DESs. The effects of HBA/HBD molar ratio, alkyl chain length, anion type, and the amine group’s substitution on the structural organization of the DESs were systematically investigated. Moreover, the influence of water addition on the structural properties of selected DESs (TBAB with AP, MAE, or BAE at a 1:6 molar ratio) was explored. These structural features were then correlated with previously reported experimental data. To complement the classical simulations, ab initio molecular dynamics simulations were conducted on the same TBAB-based systems, enabling the analysis of electronic structure phenomena, including RDFs, dipole moment distributions, and charge transfer. Furthermore, experimental large-angle X-ray scattering (LAXS) data collection and analysis were performed in terms of the simulated structural data. This multi-scale approach provides a detailed understanding of the structural and electronic characteristics governing the behavior of alkanolamine-based DES. Full article

Two-dimensional antimonene has recently emerged as a promising electrocatalytic platform; however, its oxygen reduction reaction (ORR) activity and modulation strategies remain largely unexplored. Herein, density functional theory (DFT) calculations are employed to systematically investigate ORR catalysis on antimonene co-doped with transition metal (TM) and nonmetal (C, P) dual atoms. The results reveal that Pd@C–Sb, Pt@C–Sb, and Pd@P–Sb exhibit remarkably enhanced ORR activity, delivering low overpotentials of 0.31 V, 0.32 V, and 0.38 V, respectively, significantly outperforming their single-atom-doped counterparts. Mechanistic analyses demonstrate that nonmetal dopants induce strong synergistic interactions with TM centers, leading to charge redistribution and effective regulation of the TM d-band center, which optimizes the adsorption energetics of key ORR intermediates. Notably, the number of d-electrons of TM atoms is identified as a reliable electronic descriptor governing intermediate binding strength and catalytic activity. Furthermore, ab initio molecular dynamics simulations confirm the excellent thermodynamic stability of the optimized dual-atom catalysts. This work elucidates the atomic-scale origin of synergistic enhancement in dual-atom-doped antimonene and provides a rational design strategy for high-performance ORR electrocatalysts based on two-dimensional main-group materials. Full article

Isosymmetric phase transitions driven by subtle hydrogen-bond rearrangements remain challenging for periodic density functional theory (DFT), particularly when energy differences between polymorphs are small. Resorcinol represents an interesting case in which the α and β polymorphs crystallize in the same space group and differ primarily in hydroxyl orientation and hydrogen-bond topology. In this work, the α–β phase transition was systematically investigated using periodic DFT calculations under ambient and elevated pressure. A broad set of exchange–correlation functionals combined with different dispersion corrections was benchmarked against experimental structural and energetic data. Dispersion-corrected methods were essential for reproducing lattice parameters and the pressure-induced inversion of stability. PBESOL with Tkatchenko–Scheffler dispersion provided the most consistent agreement with the experiment and was therefore used for phonon and ab initio molecular dynamics simulations. Phonon-derived thermodynamic analysis revealed a delicate enthalpy–entropy balance governing the transition, strongly affected by pressure. Dynamical simulations confirmed the instability of the α phase under compression, demonstrating the cooperative nature of this hydrogen-bond-driven isosymmetric transformation. Full article

Potassium superoxide (KO₂) can form during the oxidation of residual potassium in NaK-contaminated cold traps of sodium-cooled fast reactors. Its strong oxidizing nature, combined with limited thermal stability, raises safety concerns during shutdown and maintenance. Here, we integrate first-principles calculations with experiments to clarify the facet stability, temperature-driven surface evolution, and stepwise thermal decomposition of KO₂. Guided by the tetragonal I4/mmm crystal symmetry of bulk KO₂, symmetry-non-equivalent low-index facets and relevant surface terminations were systematically evaluated to identify physically meaningful exposed surfaces. Ab initio molecular dynamics (AIMD) simulations further show that heating induces progressive surface amorphization and enhanced oxygen mobility, accompanied by the emergence of shortened O-O bonds and outward migration of oxygen species. Kinetic analysis using the climbing-image nudged elastic band (CI-NEB) method indicates that oxygen evolution is preferentially mediated by O₂ release rather than atomic oxygen escape. Differential scanning calorimetry (DSC) reveals two endothermic events consistent with sequential decomposition, while X-ray diffraction (XRD) confirms the transformation of KO₂ into K₂O. Collectively, these results provide an atomistic-to-macroscopic understanding of KO₂ decomposition, offering practical guidance for defining safer preheating windows and handling strategies for NaK-contaminated components. Full article

We investigate the defect-dependent electronic structure and gas-sensing potential of cubic α-CsPbI₃ using first-principles density functional theory and nonadiabatic molecular dynamics. Among the intrinsic defects, interstitials, vacancies, antisites, and switches studied, the I_Pb and Pb_I antisite defects exhibit transition energy levels near the middle of the band gap, thus functioning as deep traps. Short-term adsorption of ammonia selectively modifies the electronic structure, coordinating with Pb at Pb_I sites and Cs at I_Pb sites, significantly altering recombination pathways. Detailed analysis reveals that NH₃ reduces anharmonicity at I_Pb defects, enabling enhanced recombination at elevated temperatures, while trap-assisted recombination dominates at room temperature. Other analytes, including CH₃NH₂ and NO₂, show negligible impact on the band gap or recombination dynamics, highlighting the potential selectivity of NH₃ interactions. Ab initio nonadiabatic molecular dynamics simulations at 300 K and 600 K further demonstrate temperature-dependent modulation of carrier lifetimes, with NH₃ accelerating recombination at ambient conditions and suppressing certain pathways at higher temperatures. These findings suggest that α-CsPbI₃ can serve as a selective and sensitive ammonia sensor over a broad temperature range and offer insights for ammonia detection under industrially relevant conditions. Full article

Deposition of amorphous boron (a-B) onto Si substrates via chemical decomposition of B₂H₆ molecules produces a-B/Si, heterojunctions which are the core parts of photodetectors used in vacuum ultraviolet (VUV) and potentially in extreme ultraviolet (EUV) lithography. However, fundamental questions regarding the limit on the thickness of the deposited a-B thin films and the intrinsic electronic nature of the B atoms adjacent to the Si substrate remain unanswered. Here we investigated the local structural and electronic properties of atomic-thin a-B layers at the Si{001} substrates using ab initio molecular dynamics (AIMD) techniques. The investigation revealed a rich variety of local chemical bonding and consequently interfacial electronic properties. For thin a-B layer(s)/Si systems, most of the a-B atoms at the interface formed (-B-Si-B-Si-) chains on the Si{001} surface. These B atoms were found to occupy the positions of the missing Si atoms and were bonded to the surficial Si atoms. The surficial Si atoms predominantly have two B neighbors. Localized defect states at the Fermi level for the interfacial Si and B atoms were found in the pseudo-gap. These states have a major influence on the electrical properties of the device. The predicted minimum thickness of the a-B films is about 1 to 2 nm, a useful metric for the manufacturing of a-B/Si devices. The information obtained here further helps us to understand the working mechanisms of a-B/Si interfaces for photon detection and constructing new core devices for potential applications in the field of metal/semiconductor heterojunctions for photon detection, photovoltaics, Schottky diodes and semiconductor devices. Full article

Dissolution of iron oxides in water plays a critical role in corrosion, mineral cycling, and surface reactivity; yet, the atomic-scale mechanisms governing Fe release remain poorly understood. Here, we employ ab initio molecular dynamics and well-tempered metadynamics simulations to investigate the stepwise dissolution of surface Fe atoms from the -Fe₂O₃(0001) surface in aqueous solution. The dissolution process initiates from a stable surface configuration in which Fe is coordinated to three lattice oxygen atoms and one water molecule. It proceeds through a series of metastable states involving additional water coordination, proton-assisted Fe-O bond weakening, and eventual detachment from the substrate. The first major transition, requiring 46.5 kJ/mol, involves breaking the hydrogen-bonding net and overcoming steric hindrance to allow adsorption of a second water molecule. Intermediate barriers (10.9–30.3 kJ/mol) are associated with further coordination and bond cleavage steps. In contrast, the final release of Fe into the solution, corresponding to a state coordinated with four water molecules and no lattice oxygen, exhibits a much higher free-energy barrier of ~93.0 kJ/mol. This barrier arises from the formation of a rigid hydrogen-bonded water cage and the loss of proton access to the remaining surface oxygen site, as confirmed by radial distribution function analysis. Our findings reveal why -Fe₂O₃(0001) is highly resistant to complete dissolution yet prone to surface roughening, defect formation, and adatom structures under aqueous conditions. Full article

High-entropy alloys (HEAs) have rapidly evolved from a seminal concept in 2004 to a mainstream materials science frontier, witnessing exponential growth since 2010. To date, the preparation and research methods for HEAs have undergone substantial diversification, the systems have been optimized, and their application scope has widely broadened. Herein, we provide a systematic review of various synthesis methodologies, including mechanical alloying, vacuum smelting, magnetron sputtering, and additive manufacturing. This paper meticulously summarizes a series of findings on the crucial properties of HEAs, such as mechanical properties, wear resistance, and corrosion resistance, as well as functional properties, including irradiation resistance, hydrogen storage capacity, and biocompatibility. In addition, this review explores the promising applications of HEAs in fields such as aerospace and ocean engineering. Modeling techniques applicable to HEAs, namely ab initio molecular dynamics simulations and CALPHAD modeling, are introduced and discussed. Finally, despite significant successes, the current shortcomings of HEAs, as well as future opportunities and challenges, are outlined. In summary, this review aims to offer both theoretical references and practical guidelines for the rapid evolution of HEAs. Full article

The stability of perovskite materials in humid conditions significantly hinders their practical deployment. This study employed ab initio molecular dynamics (AIMD) simulations based on the Car–Parrinello approach to elucidate the adsorption mechanisms within two systems: CH₃NH₃PbI₃-15O₂-2H₂O and CH₃NH₃PbI₃-15O₂-5H₂O. The findings indicate that in the system with a higher water content (5H₂O), the degradation of the perovskite skeleton is more severe. Additionally, the adsorption energy of oxygen molecules significantly increases, along with more pronounced charge transfer between the oxygen and the perovskite material. The study also reveals that although water molecules contribute to the damage of the perovskite skeleton, oxygen molecules are the primary culprits. These insights not only clarify the specific impacts of various components in a mixed-gas environment on perovskite stability but also provide an essential theoretical basis for future modifications and optimizations of perovskite materials. Full article

The interaction between water and metallic interfaces is crucial in many fields, and accurate modeling requires good parametrizations using reference data. In classical molecular dynamics (MD), an important part of this interaction is described using the Lennard–Jones (LJ) potential. However, previously reported LJ parameters are not always optimal for capturing the metal/water interactions observed in ab initio descriptions such as density functional theory (DFT). Therefore, well-tailored LJ parameters are necessary to improve the description of water structuring metals in classical MD. The usual route for obtaining LJ parameters involves energetic analysis, where the energies of various structures are obtained via DFT calculations and then matched with the energies obtained using the LJ potentials by varying the sigma/epsilon parameters. Here, we show a different approach to fit LJ parameters for metal/water interactions, based on structural analysis. We report several classical MD simulations for gold/water, varying the sigma/epsilon parameters, comparing the resulting water structuring with that obtained using DFT. Additionally, we test these parameters in quantum mechanics/molecular mechanics (QM/MM) MD simulations, where electrostatic interactions are enabled. Our results demonstrate that the proposed approach can improve the LJ parameters reported in the literature and potentially develop parameters for more complex systems where the water structure above metallic surfaces plays a significant role. Finally, within this proposed approach, the water density profile obtained in hybrid QM/MM calculations, where water is treated as MM at a substantially reduced cost, closely matches the description it would have if treated as QM. Full article

Nano-aluminum (nAl), characterized by its high combustion enthalpy and enhanced reactivity, serves as a critical component in advanced energetic materials like solid propellants and micro-ignition devices. However, the atomic-scale mechanisms governing its core–shell structure evolution, oxidation dynamics, and interfacial interactions remain elusive to experimental probes due to spatiotemporal limitations. Molecular dynamics (MD) simulations, particularly the synergistic use of a ReaxFF reactive force field (for large-scale systems) and ab initio MD (for electronic-level accuracy), have emerged as a powerful tool to overcome this barrier. This review systematically delineates the oxidation mechanisms and core–shell structure regulation of nAl, with a focus on the multi-scale simulation paradigm integrating DFT, AIMD, and ReaxFF MD that directly supports nAl research. It critically examines the pivotal role of MD simulations in guiding the surface modification of nAl, elucidating combustion mechanisms at the atomic level, and designing interfaces in energetic composite systems. By synthesizing recent advances (2022–2025), this study establishes a clear structure–property relationship between microscopic features and macroscopic performance of nAl. Furthermore, it identifies prevailing challenges, including simulations under multi-physics loading, multi-scale bridging, and quantitative experiment-simulation validation that specifically affect nAl-based energetic systems. Finally, future research directions are prospected, encompassing the development of machine learning-empowered force fields tailored for nAl systems, multi-scale and multi-field coupling simulation frameworks targeting nAl applications, and closed-loop experiment-simulation systems for nAl-based energetic materials. This review aims to provide fundamental insights and a technical framework for the rational design and engineering application of nAl-based energetic materials in fields such as aerospace propulsion. Full article

With the increasing adoption of traveling grate machines, increasing the proportion of pellets in blast furnace burdens has become a key strategy for reducing carbon emissions in ironmaking. Magnetite (Fe₃O₄) is not only the core raw material for pellet production but also serves as an important transition metal oxide catalyst, widely used in various fields due to its unique electronic structure and surface activity. This study employed density functional theory (DFT) and ab initio molecular dynamics (AIMD) to simulate the oxidation process of a Ca-doped Fe₃O₄ (110) surface at 1073 K, revealing the inhibition mechanism of the gangue element Ca and its impact on surface catalytic activity at the atomic scale. The results demonstrate that Ca segregates on the Fe₃O₄ surface, where it adsorbs and activates O₂ molecules, thereby delaying O₂ migration to active iron bridge sites and subsequent dissociation, which ultimately inhibits the oxidation kinetics. Electronic structure analysis indicates that the breakage of the O–O bond is accompanied by a sharp decrease in system energy (stabilizing at approximately −509 eV); it also clearly elucidates the charge transfer process and the mechanism of Fe-O bond formation during this exothermic reaction. This research provides a theoretical foundation for the development of fluxed pellets and high-temperature-resistant catalysts. Full article

Constructing two-dimensional (2D) novel materials using superatoms as building blocks is currently a highly promising research field. In this study, by employing an oxidation strategy and based on first-principles calculations, we successfully predicted two types of 2D borides, namely B₁₂X₂H₆ (X=O, S), with icosahedral B₁₂ serving as their core structural unit. Ab initio molecular dynamics simulations demonstrated that these two borides exhibit exceptionally high structural stability, retaining their original structural characteristics even under extreme temperature conditions as high as 2200 K. Electronic structure calculations revealed that B₁₂O₂H₆ and B₁₂S₂H₆ are both wide-bandgap indirect semiconductors, with bandgap widths reaching 4.92 eV and 5.25 eV, respectively. Analysis via deformation potential theory showed that the phonon-limited carrier mobilities of B₁₂X₂H₆ can reach up to 1469 cm²V⁻¹s⁻¹ (for B₁₂O₂H₆) and 635 cm²V⁻¹s⁻¹ (for B₁₂S₂H₆). Notably, the surfaces of B₁₂X₂H₆ demonstrate excellent migration performance for alkali metal ions, with migration barriers as low as 0.15 eV (for B₁₂O₂H₆) and 0.033 eV (for B₁₂S₂H₆). This study not only expands the family of 2D materials based on B₁₂ superatoms but also provides a solid theoretical foundation for the potential application of B₁₂X₂H₆ in the field of low-dimensional materials. Full article

Ligands L1 and L2 are composed, respectively, by a diethylenetriamine or a dipropylenetriamine moiety linked at their extremities to anthracene units through methylene bridges and form stable 1:1 complexes with Zn(II), in which the metal is coordinated by all three nitrogens of the ligands. Zn(II) binding by L1 leads to a marked enhancement of the fluorescence emission, thanks to the inhibition of the photoinduced electron transfer (PET) process from the benzylic amine groups of the triamine sub-unit to the excited fluorophore, which normally quenches the emission of fluorescent polyamine receptors. Conversely, the emission of L2 is somewhat quenched by Zn(II) binding likely due—as also indicated by ab initio calculations and molecular dynamics simulations—to the formation of cation π quenching contacts between the metal and the anthracene moieties that overcome the effects of PET inhibition. The Zn(II) complexes of both ligands are able to bind ketoprofen (KP) in its anionic form, thanks to the formation of COO⁻—Zn(II) coordinative bonds, to form [KPZnL]⁺ and [(KP)₂ZnL] (L = L1 or L2) ternary adducts. While KP binding to [ZnL2]²⁺ enhances the fluorophore emission, coordination of KP to [ZnL1]²⁺ slightly reduces the anthracene emission, due, once again, to the formation in the L1 ternary complexes of marked cation π contacts. Full article