Ab initio thermodynamics of fcc H-Zr and formation of hydrides.
Saved in:
| Title: | Ab initio thermodynamics of fcc H-Zr and formation of hydrides. |
|---|---|
| Authors: | Besson, R.1, Candela, R.1 |
| Source: | Computational Materials Science. Mar2016, Vol. 114, p254-263. 10p. |
| Subjects: | Ab initio quantum chemistry methods, Face centered cubic structure, Zirconium compounds, Hydrides, Chemical stability, Free energy (Thermodynamics), Low temperatures, Phase diagrams |
| Abstract: | In order to elucidate the currently debated stability of zirconium hydrides, the energetics of fcc H-Zr was investigated by means of ab initio-based cluster expansions (CEs) including the effect of long-range interactions, the latter being possibly important due to the interstitial H site occupancy in fcc-Zr. Allowing a detailed temperature- and composition-dependent evaluation of the configuration part of free energies in fcc H-Zr, our modelling provides new insights into the controversial properties of the γ-ZrH compound: (i) at low temperature, γ is metastable with respect to α-Zr + ε-ZrH 2− x , (ii) there exists a temperature domain around 500 K in which γ becomes stable, in agreement with recent experiments, (iii) contrasting with the ill-defined off-stoichiometry of the stable δ-ZrH y ( y ∼ 1.5) and ε-ZrH 2− x hydrides, γ is a line-compound undergoing a γ → δ order/disorder transition at moderate temperature (∼800 K), (iv) the γ composition domain corresponds to a strong failure of the usual random approximation for the configurational entropy. Relying on a large set of ab initio data, our results also reveal an intricate energetic behaviour of fcc H-Zr around the δ domain. This complex behaviour could not be not reliably captured by CE modelling, which implies that, contrary to experiments, our proposed theoretical H-Zr phase diagram contains no δ + ε domain. Moreover, the coupling between phonons and chemical order, much more significant at ZrH composition than for higher H contents, may be responsible for a lowering of the order–disorder transition temperature of γ. Our work therefore indicates that including phonons into CEs should be a promising direction for high-quality modelling of Zr hydrides. [ABSTRACT FROM AUTHOR] |
| Copyright of Computational Materials Science is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Engineering Source |
| FullText | Text: Availability: 0 |
|---|---|
| Header | DbId: egs DbLabel: Engineering Source An: 112674325 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
| IllustrationInfo | |
| Items | – Name: Title Label: Title Group: Ti Data: Ab initio thermodynamics of fcc H-Zr and formation of hydrides. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Besson%2C+R%2E%22">Besson, R.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Candela%2C+R%2E%22">Candela, R.</searchLink><relatesTo>1</relatesTo> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Computational+Materials+Science%22">Computational Materials Science</searchLink>. Mar2016, Vol. 114, p254-263. 10p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Ab+initio+quantum+chemistry+methods%22">Ab initio quantum chemistry methods</searchLink><br /><searchLink fieldCode="DE" term="%22Face+centered+cubic+structure%22">Face centered cubic structure</searchLink><br /><searchLink fieldCode="DE" term="%22Zirconium+compounds%22">Zirconium compounds</searchLink><br /><searchLink fieldCode="DE" term="%22Hydrides%22">Hydrides</searchLink><br /><searchLink fieldCode="DE" term="%22Chemical+stability%22">Chemical stability</searchLink><br /><searchLink fieldCode="DE" term="%22Free+energy+%28Thermodynamics%29%22">Free energy (Thermodynamics)</searchLink><br /><searchLink fieldCode="DE" term="%22Low+temperatures%22">Low temperatures</searchLink><br /><searchLink fieldCode="DE" term="%22Phase+diagrams%22">Phase diagrams</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: In order to elucidate the currently debated stability of zirconium hydrides, the energetics of fcc H-Zr was investigated by means of ab initio-based cluster expansions (CEs) including the effect of long-range interactions, the latter being possibly important due to the interstitial H site occupancy in fcc-Zr. Allowing a detailed temperature- and composition-dependent evaluation of the configuration part of free energies in fcc H-Zr, our modelling provides new insights into the controversial properties of the γ-ZrH compound: (i) at low temperature, γ is metastable with respect to α-Zr + ε-ZrH 2− x , (ii) there exists a temperature domain around 500 K in which γ becomes stable, in agreement with recent experiments, (iii) contrasting with the ill-defined off-stoichiometry of the stable δ-ZrH y ( y ∼ 1.5) and ε-ZrH 2− x hydrides, γ is a line-compound undergoing a γ → δ order/disorder transition at moderate temperature (∼800 K), (iv) the γ composition domain corresponds to a strong failure of the usual random approximation for the configurational entropy. Relying on a large set of ab initio data, our results also reveal an intricate energetic behaviour of fcc H-Zr around the δ domain. This complex behaviour could not be not reliably captured by CE modelling, which implies that, contrary to experiments, our proposed theoretical H-Zr phase diagram contains no δ + ε domain. Moreover, the coupling between phonons and chemical order, much more significant at ZrH composition than for higher H contents, may be responsible for a lowering of the order–disorder transition temperature of γ. Our work therefore indicates that including phonons into CEs should be a promising direction for high-quality modelling of Zr hydrides. [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Computational Materials Science is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
| PLink | https://search.ebscohost.com/login.aspx?direct=true&site=eds-live&db=egs&AN=112674325 |
| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1016/j.commatsci.2015.12.043 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 10 StartPage: 254 Subjects: – SubjectFull: Ab initio quantum chemistry methods Type: general – SubjectFull: Face centered cubic structure Type: general – SubjectFull: Zirconium compounds Type: general – SubjectFull: Hydrides Type: general – SubjectFull: Chemical stability Type: general – SubjectFull: Free energy (Thermodynamics) Type: general – SubjectFull: Low temperatures Type: general – SubjectFull: Phase diagrams Type: general Titles: – TitleFull: Ab initio thermodynamics of fcc H-Zr and formation of hydrides. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Besson, R. – PersonEntity: Name: NameFull: Candela, R. IsPartOfRelationships: – BibEntity: Dates: – D: 01 M: 03 Text: Mar2016 Type: published Y: 2016 Identifiers: – Type: issn-print Value: 09270256 Numbering: – Type: volume Value: 114 Titles: – TitleFull: Computational Materials Science Type: main |
| ResultId | 1 |
