To extend the study of vanadium disulfide (VS2) nanostructures beyond the system size and simulation time limits of ab initio methods, we introduce a new ReaxFF parameter set: ReaxFF VS2-2025. The ReaxFF VS2-2025 potential was parametrized against extensive quantum mechanical and experimental data, and it can accurately capture the energetic and physicochemical properties of two-dimensional (2D) VS2. Using this force field in molecular dynamics (MD) simulations, uniaxial tensile tests on 2H-VS2 yield Young’s moduli of 122.5 ± 0.1 GPa in the zigzag direction and 108.0 ± 0.2 GPa in the armchair direction, revealing an anisotropic elastic response. Defect formation energy calculations indicate that single sulfur vacancies are the most energetically favorable defect across the entire range of the allowed chemical potential for V and S, and single vanadium vacancies are more favorable than sulfur divacancies in sulfur-rich conditions, all consistent with density functional theory results. The melting simulations yield a melting temperature of 920 ± 50 K for monolayer 2H-VS2. Notably, during the melting process, VS2 shows a transient amorphous structure that has a drop in potential energy. This amorphous structure even shows a lower potential energy than that of the 2D VS2 in a follow-up relaxation at 0 K. These MD simulations confirm that the 2D 2H-VS2 is indeed metastable, explaining why synthesizing layered VS2 is experimentally difficult. Overall, this study offers insights into the structural and physicochemical behavior of VS2, providing a foundation for the rational design of VS2-based materials for catalytic, electronic, and electrochemical applications.
Matin Salimi Irdmusa, S. Dwivedi, Firdevs Gür et al.· Journal of Physical Chemistr...· 0 citations
To predict the thermochemistry and thermophysical properties and oxidation mechanisms of titanium diboride (TiB2), we have developed a ReaxFF reactive force field in which the parameters are trained against a set of quantum mechanics data, including the heats of formation and elastic properties for various titanium boride phases, as well as heats of formation of various titanium oxide and boron oxide phases. The developed ReaxFF accurately reproduces the formation energies, relative stability, and elastic properties of these phases. To demonstrate the applicability of our developed ReaxFF force field, we performed ReaxFF-based molecular dynamics simulations to evaluate thermal expansion and melting behavior and validated the results against published experimental data. The thermal expansion simulations reflected the experimentally observed anisotropic behavior, demonstrating greater expansion along the c-axis compared to the a-axis, and showed good agreement in volume expansion measurements. The predicted bulk melting temperature of 3120.87 K is consistent with experimental values (3063–3498 K), while a lower surface melting point of 3049.20 K was observed due to reduced atomic coordination. Moreover, the oxidation behavior of TiB2 was investigated using molecular dynamics simulations. To accelerate the oxidation process within the accessible MD time scales, we employed elevated oxygen concentrations and high-temperature conditions. Additionally, replica exchange molecular dynamics (REMD) simulations were conducted at a temperature of 1970 K, corresponding to experimental oxidation conditions. The simulations revealed that oxidation was initiated with the formation of titanium oxides, consistent with the lower formation energy of TiO2 compared to B2O3. Notably, the titanium oxide formed during the REMD simulations mostly resembled the TiO2 phase in terms of crystallinity. Smaller boron oxide species were also observed through REMD simulations. These results confirm that the developed ReaxFF potential reliably models both the thermochemical and thermophysical behavior of TiB2, as well as complex oxidation mechanisms, making it an accurate and computationally inexpensive tool for simulating high-temperature ceramic materials.
M. Mirakhory, S. Ness, S. McCormack et al.· Journal of Physical Chemistr...· 0 citations
Bridging atomically precise materials design with scalable membrane manufacturing remains a central challenge in separation science. Two-dimensional covalent organic frameworks (2D COFs) offer tunable porosity and chemistry, but poor crystallinity and processability have limited their performance in membranes. Here we demonstrate that incorporating single-crystalline 2D COFs into anodic aluminum oxide supports and scalable mixed-matrix membrane enables exceptional separation performance, achieving ultrahigh permeance (MMM-SC-0.6: 8764 and 4531 L m–2 h–1 bar–1 for hexane and methanol, respectively) and near-quantitative rejection of nanoscale solutes. Reactive force field simulations through a multilayer COF model reveal the origins of rapid solvent transport and size selectivity through steric gating. These results establish highly crystalline COFs as practical, high-performance membrane materials and point to new routes for energy-efficient separations across chemical, environmental, and industrial technologies.
Jasasmita Das, Yun Kyung Shin, Beatrice Bartolomei et al.· Journal of the American Chem...· 0 citations
We use cookies to run the site and, with your consent, for analytics and to show ads.
See our Cookie Policy.
