Despite decades of study, several key aspects of the Al-H system remain the subject of considerable debate. In an effort to elucidate some of these unknowns, we perform a systematic study of this system using first-principles density-functional calculations. We show that generalized gradient approximation (GGA) calculations provide an accurate picture of energetics, phase stability and structure, diffusion, and defect binding in the Al-H system. A series of calculations for hydrides in the M-H systems (M=Al, Ba, Ca, K, Mg, La, Li, Na, Ni, Pd, Sc, Sr, Ti, V, and Y) also shows that the GGA calculations are a quantitatively accurate predictor of hydride formation energies. For Al-H, we find: (i) In agreement with experiment, the observed metastable hydride, ${\mathrm{AlH}}_{3}$ is found to have a small, negative formation enthalpy at ambient conditions, but a strongly positive formation free energy. (ii) Linear response calculations of ${\mathrm{AlH}}_{3}$ yield vibrational frequencies, phonon densities of states (DOS), and heat capacities in excellent agreement with experimental measurements, and suggest the need for a reinterpretation of measured phonon DOS. (iii) Atomic relaxation and anharmonic vibrational effects both play an important role in the tetrahedral versus octahedral interstitial site preference of H in Al. (iv) The calculated heat of solution of H in the preferred tetrahedral site is large and positive (+0.71 eV), consistent with experimental solubility data and with Al as an endothermic hydrogen absorber. (v) Interstitial H interacts strongly with Al vacancies $(\ensuremath{\square}),$ with a calculated H-$\ensuremath{\square}$ binding energy of 0.33 eV. (vi) In the absence of vacancies, the calculated migration energy of H between the tetrahedral and octahedral interstitial sites is 0.18 eV, but for H migrating away from an Al vacancy, the migration energy increases to 0.54 eV. Vacancy trapping of H can therefore provide an explanation for observed disparate H migration barriers.

Hydrogen in aluminum: First-principles calculations of structure and thermodynamics

http://www.issp.ac.ru/lhpp/PapersAntonov/134.pdf

Phase transformations, crystal and magnetic structures of high-pressure hydrides of d-metals

Aluminum hydride for solid-state hydrogen storage: Structure, synthesis, thermodynamics, kinetics, and regeneration

Hydrides of iron and iron-based alloys are thermodynamically stable only at hydrogen pressures in the gigapascal range and rapidly lose hydrogen under ambient conditions. At low temperatures, however, these hydrides can be retained in a metastable state at atmospheric pressure after being cooled under high pressure to liquid nitrogen temperature. This review will discuss the current state of studies on phase transformations in the Fe?H and related systems and also on the composition, crystal structure and physical properties of the hydrides, both under high hydrogen pressures and in the 'quenched' metastable state at ambient pressure. The studies at ambient pressure include magnetization measurements, x-ray and neutron diffraction, M?ssbauer spectroscopy and inelastic neutron scattering. In the sections on M?ssbauer and structural investigations of hydrides of Fe?Cr and Ni?Fe alloys new experimental results will be presented.

/pdf/high-pressure-hydrides-of-iron-and-its-alloys-49nsq5mra2.pdf

High-pressure hydrides of iron and its alloys

The effects of high-pressure hydrogen and deuterium charging on the structure of AISI type 304 and AISI type 310 austenitic stainless steels have been investigated by neutron and X-ray diffraction. Rietveld analyses of the neutron diffraction data revealed that hydrogen atoms occupy exclusively the octahedral interstitial sites in both steels. No phase transformations have been observed in 310 stainless steel within the whole range of hydrogen-to-metal atomic ratios H/Me up to ≈ 1. In 304 stainless steel, the formation of ɛ-martensite was observed not only after hydrogenation at 3.0 GPa (H/Me = 0.56), but also after applying a pressure of 4.0 GPa without hydrogen. The results differ significantly from published studies on cathodically hydrogenated samples, where high amounts of ɛ-martensite were observed in both steels. High-pressure hydrogenation and cathodic hydrogen charging result in different phase transformation behaviour. The discrepancies can be explained by different hydrogen distributions resulting in quite different stress states.

https://ftp.ncnr.nist.gov/instruments/fans/fans_pdf_files/hoelzel2004.pdf

Effects of high-pressure hydrogen charging on the structure of austenitic stainless steels

T-P phase diagram of the Mn-H system at pressures to 4.4 GPa and temperatures to 1000 °C

The lattice dynamics of and were studied by inelastic neutron scattering (INS). The hydrogen optic modes in the INS spectra were shown to form a broad structured band which exhibited an harmonic isotopic behaviour. In contrast, the low-energy part of the phonon spectra, formed mainly by the vibrations of the metal atoms, showed pronounced anharmonicity. The temperature dependence of the heat capacity derived from the INS data agrees with the available experimental dependence at 50 - 150 K.

/pdf/neutron-spectroscopy-of-aluminium-trihydride-4a8vru1hgl.pdf

Neutron spectroscopy of aluminium trihydride

An investigation was made of fuel films in targets used in experiments on laser thermonuclear fusion in Iskra-4 and Iskra-5 systems. These films were formed from condensed deuterium and a deuterium—tritium mixture, and also from metal hydrides and polyethylene containing deuterium and tritium.

http://iopscience.iop.org/article/10.1070/QE1994v024n02ABEH000040/pdf

Films containing heavy hydrogen isotopes in laser thermonuclear fusion targets

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

N A Chirin

Author Tools

Chat about Author

Papers

T-P phase diagram of the Mn-H system at pressures to 4.4 GPa and temperatures to 1000 °C

Neutron spectroscopy of aluminium trihydride

Films containing heavy hydrogen isotopes in laser thermonuclear fusion targets