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Ca(AlH₄)₂, CaAlH₅, and CaH₂+6LiBH₄: Calculated dehydrogenation enthalpy, including zero point energy, and the structure of the phonon spectra

Marashdeh, Ali; Frankcombe, Terry J.

Description

The dehydrogenation enthalpies of Ca(AlH₄)₂, CaAlH₅, and CaH₂+6LiBH₄ have been calculated using density functional theory calculations at the generalized gradient approximation level. Harmonic phonon zero point energy (ZPE) corrections have been included using Parlinski's direct method. The dehydrogenation of Ca(AlH₄)₂ is exothermic, indicating a metastable hydride. Calculations for CaAlH₅ including ZPE effects indicate that it is not stable enough for a hydrogen storage system operating near...[Show more]

dc.contributor.authorMarashdeh, Ali
dc.contributor.authorFrankcombe, Terry J.
dc.date.accessioned2015-11-24T23:58:48Z
dc.date.available2015-11-24T23:58:48Z
dc.identifier.issn0021-9606
dc.identifier.urihttp://hdl.handle.net/1885/16709
dc.description.abstractThe dehydrogenation enthalpies of Ca(AlH₄)₂, CaAlH₅, and CaH₂+6LiBH₄ have been calculated using density functional theory calculations at the generalized gradient approximation level. Harmonic phonon zero point energy (ZPE) corrections have been included using Parlinski's direct method. The dehydrogenation of Ca(AlH₄)₂ is exothermic, indicating a metastable hydride. Calculations for CaAlH₅ including ZPE effects indicate that it is not stable enough for a hydrogen storage system operating near ambient conditions. The destabilized combination of LiBH₄ with CaH₂ is a promising system after ZPE-corrected enthalpy calculations. The calculations confirm that including ZPE effects in the harmonic approximation for the dehydrogenation of Ca(AlH₄)₂, CaAlH₅, and CaH₂+6LiBH₄ has a significant effect on the calculated reaction enthalpy. The contribution of ZPE to the dehydrogenation enthalpies of Ca(AlH₄)₂ and CaAlH₅ calculated by the direct method phonon analysis was compared to that calculated by the frozen-phonon method. The crystal structure of CaAlH₅ is presented in the more useful standard setting of P2₁/c symmetry and the phonon density of states of CaAlH₅, significantly different to other common complex metal hydrides, is rationalized.
dc.description.sponsorshipThe work presented here has been supported by an NWO grant under the ACTS Hydrogen program.
dc.publisherAmerican Institute of Physics (AIP)
dc.rightshttp://www.sherpa.ac.uk/romeo/issn/0021-9606..."Publishers version/PDF may be used on author's personal website, institutional website or institutional repository" from SHERPA/RoMEO site (as at 25/11/15). Copyright 2008 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in The Journal of Chemical Physics and may be found at https://doi.org/10.1063/1.2937917
dc.sourceThe Journal of Chemical Physics
dc.subjectKeywords: Aluminum; Crystal structure; Crystal symmetry; Dehydrogenation; Density functional theory; Enthalpy; Hydrides; Hydrogen; Hydrogen storage; Metals; Nonmetals; Phonons; Polynomial approximation; Probability density function; Standards; Thermodynamics; Ambie
dc.titleCa(AlH₄)₂, CaAlH₅, and CaH₂+6LiBH₄: Calculated dehydrogenation enthalpy, including zero point energy, and the structure of the phonon spectra
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume128
dc.date.issued2008-06-17
local.identifier.absfor030799
local.identifier.ariespublicationu4217927xPUB267
local.publisher.urlhttps://www.aip.org/
local.type.statusPublished Version
local.contributor.affiliationMarashdeh, Ali, Leiden University, Netherlands
local.contributor.affiliationFrankcombe, Terry, College of Physical and Mathematical Sciences, CPMS Research School of Chemistry, RSC General, The Australian National University
local.identifier.essn1089-7690
local.bibliographicCitation.issue23
local.bibliographicCitation.startpage234505
local.identifier.doi10.1063/1.2937917
dc.date.updated2015-12-09T09:16:04Z
local.identifier.scopusID2-s2.0-47249149812
local.identifier.thomsonID000256936700024
CollectionsANU Research Publications

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