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Li+ and H+ Diffusions in Lithium Amide and Hydride: A first-principles study
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. (Condensed Matter Theory)
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In the present work, the reaction energies of Li+ and H+ migrations with two different situations, namely inside LiNH2 and between LiNH2 and LiH are determined by the density functional theory. Our results reveal that the Li+ migrations in both cases are rather easy. However, H+ diffusion from LiNH2 to LiH is found to be more difficult than that inside LiNH2. Consequently, diffusions of Li+ and H+ inside LiNH2 are more favorable than those between LiNH2 and LiH. Finally, the migration energies of Li+ and H+ migrations in LiNH2 are determined by the nudged elastic band method and we found that Li+ and H+ migration energy barriers in LiNH2 are 0.30 and 0.58 eV, respectively.

Keyword [en]
Lithium-hydrogen-nitrogen system, reaction energy, migration energy
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-132781OAI: oai:DiVA.org:uu-132781DiVA: diva2:359148
Available from: 2010-10-26 Created: 2010-10-26 Last updated: 2012-03-29
In thesis
1. Computational Studies of Hydrogen Storage Materials: Physisorbed and Chemisorbed  Systems
Open this publication in new window or tab >>Computational Studies of Hydrogen Storage Materials: Physisorbed and Chemisorbed  Systems
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with first-principles calculations based on density functional theory to investigate hydrogen storage related properties in various high-surface area materials and the ground state crystal structures in alkaline earth dicarbide systems.

High-surface area materials have been shown to be very promising for hydrogen storage applications owing to them containing numerous hydrogen adsorption sites and good kinetics for adsorption/desorption. However, one disadvantage of these materials is their very weak interaction with adsorbed hydrogen molecules. Hence, for any feasible applications, the hydrogen interaction energy of these materials must be enhanced.  In metal organic frameworks, approaches for improving the hydrogen interaction energy are opening the metal oxide cluster and decorating hydrogen attracting metals, e.g. Li, at the adsorption sites of the host.  In covalent organic framework-1, the effects of the H2-H2 interaction are also found to play a significant role for enhancing the hydrogen adsorption energy. Moreover, ab initio molecular dynamics simulations reveal that hydrogen molecules can be trapped in the host material due to the blockage from adjacent adsorbed hydrogen molecules.

In light metal hydride systems, hydrogen ions play two different roles, namely they can behave as "promoter" and "inhibitor" of Li diffusion in lithium imide and lithium amide, respectively.  By studying thermodynamics of Li+ and proton diffusions in the mixture between lithium amide and lithium hydride, it was found that Li+ and proton diffusions inside lithium amide are more favorable than those between lithium amide and lithium hydride.

Finally, our results show that the ground state configuration of BeC2 and MgC2 consists of five-membered carbon rings connected through a carbon atom forming an infinitely repeated chain surrounded by Be/Mg ions, whereas the stable crystal structure of the CaC2, SrC2 and BaC2 is the chain type structure, commonly found in the alkaline earth dicarbide systems.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 90 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 782
Keyword
Density functional theory, Ab initio molecular dynamics, Ab initio random structure searching, Hydrogen storage materials, Alkaline earth dicarbide
National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-132875 (URN)978-91-554-7933-6 (ISBN)
Public defence
2010-12-10, Å80101, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Note
Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 712Available from: 2010-11-19 Created: 2010-10-28 Last updated: 2011-03-21Bibliographically approved

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Scheicher, RalphAhuja, Rajeev

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