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First-principles study of hydrogen storage application of Ti3C2Tx monolayer MXene
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Machine-learning and first-principles investigation of lightweight medium-entropy alloys for hydrogen-storage applications
The transition to a low-carbon economy demands efficient and sustainable energy-storage solutions, with hydrogen emerging as a promising clean-energy carrier and with metal hydrides recognized for their hydrogen-storage capacity. Here, we leverage machine learning (ML) to predict hydrogen-to-metal (H/M) ratios and solution energy by incorporating thermodynamic parameters and local lattice distortion (LLD) as key features. Our best-performing ML model provides improvements to H/M ratios and solution energies over a broad class of medium-entripy alloys (easily extendable to multi-principal-element alloys), such as Ti–Nb-X (X = Mo, Cr, Hf, Ta, V, Zr) and Co–Ni-X (X = Al, Mg, V). Ti–Nb–Mo alloys reveal compositional effects in H-storage behavior, in particular Ti, Nb, and V enhance H-storage capacity, while Mo reduces H/M and hydrogen weight percent by 40–50 %. We attributed results in molybdenum-rich alloys to slow hydrogen kinetics, as validated by our pressure-composition-temperature (PCT) isotherm experiments on pure Ti and Ti 5 Mo 95 alloys. Density functional theory (DFT) and molecular dynamics (MD) simulations also confirm that Ti and Nb promote H diffusion, whereas Mo hinders it, highlighting the interplay between electronic structure, lattice distortions, and hydrogen uptake. Notably, our Gradient Boosting Regression model identifies LLD as a critical factor in H/M predictions. Here, to aid material selection, we present two periodic tables illustrating elemental effects on (a) H 2 wt% and (b) solution energy, derived from ML, and provide a reference for identifying alloying elements that enhance hydrogen solubility and storage.
First-principles study of MXene properties with varying hydrofluoric acid concentration
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Mechanical and Electronic Properties of A1-xBxHy (A and B =Ti, Zr, Hf) Hydride Alloys: A First-principles Study
Using ab initio calculations, we investigated the mechanical and electronic properties of Ti1-xHfxHy, Ti1-xZrxHy and Zr1-xHfxTHy (x=0, 0.25, 0.5, 0.75, 1; y=1.5, 1.75, 2). The calculated results in binary hydrides show that the β-phase MH1.5[100] (M=Ti, Zr, Hf) are more stable than other possible structures. At the Fermi level, the density of states for metal d state increases with increasing the H concentration in MHy (y ranged from 1.5 to 2), which leads to the instability of their fcc structures and induces the tetragonal distortion. Ti0.75Hf0.25H1.5 and Zr0.25Hf0.75H1.5 exhibit the highest mechanical stability, while Ti0.25Zr0.75H1.5 has the lowest mechanical stability among the corresponding ternary systems considered. Moreover, the systems studied in the present work are all anisotropic and show a ductile behavior. The tetragonal distortion in Ti1-xHfxH1.5, Ti1-xZrxH1.5 and Zr1-xHfxH1.5 is not observed, retaining their fcc structures. The electronic structure of A1-xBxHy (A and B =Ti, Hf, Zr) exhibits metallic character.
First-principles phase stability in the Ti-V alloy system
Abstract not provided
Metallic nickel silicides: Experiments and theory for NiSi and first principles calculations for other phases
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Substitutional and interstitial doping in LaCo5 system for the development of hard magnetic properties: A first principles study
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Be₂C as a neutron moderator for molten salt reactors: A first-principles study of structural, electronic, and defect properties
Beryllium carbide (Be 2 C), valued for its high neutron moderation efficiency and low absorption cross section, is a promising high-temperature neutron moderator for molten salt reactors. Its practical adoption, however, demands significant technological maturation, requiring comprehensive theoretical and experimental studies of its response to different conditions, including high temperature and irradiation. Here, we report initial results on the fundamental properties and radiation-induced defects of Be 2 C, focusing on antisites, vacancies, interstitial atoms, and Frenkel pairs in the Be and C sublattices. Using density functional theory (DFT) and ab initio molecular dynamics (AIMD), we calculate the defects formation and binding energies, evaluating their dependence on the supercell size, charge states, and chemical environment. In general, carbon defects exhibit higher formation energies, greater sensitivity to cell size, and stronger impacts on the density of states compared to beryllium defects, with charged state the effects being more pronounced. Static DFT reveals multiple metastable interstitial configurations, while AIMD identifies ground states as C-C <100> dumbbells and octahedral Be interstitials. In conclusion, the diversity of metastable configurations and defect states complicates the diffusion mechanisms, requiring further molecular dynamics analysis to elucidate the mechanisms and rates of radiation-induced atomic transport, as well as the structural stability of Be2C.
First principles, microkinetic, and experimental analysis of Lewis acid site speciation during ethanol dehydration on Sn-Beta zeolites
Density functional theory calculations are combined with kinetic measurements of ethanol dehydration to diethyl ether to identify the relative catalytic contributions of structurally distinct speciations of Sn sites in zeolite Beta frameworks. The structural complexities of the Beta framework require nonstandard techniques for entropy and energy calculations, including consideration of anharmonic effects in vibrational modes, employment of quasi-harmonic densities of states methods to evaluate entropies, and use of hybrid density functionals to evaluate binding energies. Calculated energies and entropies are used to construct a microkinetic model that is iteratively refined to identify all kinetically and thermodynamically sensitive reaction steps and intermediates which are subsequently treated with the higher-level methods. The rate and equilibrium constants obtained from this tiered approach agree well with measured reaction orders in ethanol and water. Site balances provide evidence for the interconversion of Sn sites between “closed” configurations that are tetra-coordinated to the framework, open configurations formed by hydrolysis that are tri-coordinated to the framework and contain a hydroxyl ligand and proximal silanol group (“hydroxy-open”), and open tri-coordinate configurations formed by reaction with ethanol, yielding an ethoxy ligand and proximal silanol group (“ethoxy-open”). Closed, hydroxy-open, and ethoxy-open Sn sites adsorb ethanol via distinct modes and react via distinct pathways, with the consequence that prevalent dehydration pathways depend on the speciation of Sn sites under reaction conditions. The kinetic modeling indicates that, under the conditions studied (404 K, 0.5–35 kPa ethanol, 0.1–50 kPa water), bimolecular dehydration on the closed Sn site is the sole kinetically-relevant step, and ethanol, ethanol-ethanol dimers, and ethanol-water dimers are the most abundant surface intermediates. In conclusion, these results highlight the importance of considering the distribution of heteroatom coordination modes to zeolite frameworks under reaction conditions, as well as pathways for their interconversion in the presence of reacting molecules, to obtain more robust mechanistic and kinetic interpretations of catalytic pathways in Lewis acid zeolites.
First principles micro-kinetic model of catalytic non-oxidative dehydrogenation of ethane over close-packed metallic facets
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Quantifying uncertainties in first-principles alloy thermodynamics using cluster expansions
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