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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,351 records · Page 75
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

First principles density functional theory study of Pb doped α-MnO 2 catalytic materials

Here, the impact of Pb in the tunnels of manganese oxide octahedral molecular sieves on chemical state of Mn species and lattice oxygen were investigated utilizing density functional theory calculations. The results show that the Pb dopant in the tunnels of OMS-2 could reduce the average valence states of Mn. The lower energy required for bulk oxygen defects formation in Pb-OMS-2 validates the activation of lattice oxygen by inclusion of tunnel dopant. The inclusion of Pb promotes the catalytic oxidation activity of OMS-2 by reducing the energy required for the surface lattice oxygen migration during the Mars – van Krevelen oxidation process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

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.

08 HYDROGEN↗
DOE OSTI2013

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.

Ab initio calculation↗