kth.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Iron-silica interaction at extreme conditions and the electrically conducting layer at the base of Earth's mantle
Bayerisches Geoinstitut, Universität Bayreuth.
Bayerisches Geoinstitut, Universität Bayreuth.
Bayerisches Geoinstitut, Universität Bayreuth.
Bayerisches Geoinstitut, Universität Bayreuth.
Show others and affiliations
2003 (English)In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 422, no 6927, p. 58-61Article in journal (Refereed) Published
Abstract [en]

The boundary between the Earth's metallic core and its silicate mantle is characterized by strong lateral heterogeneity and sharp changes in density, seismic wave velocities, electrical conductivity and chemical composition(1-7). To investigate the composition and properties of the lowermost mantle, an understanding of the chemical reactions that take place between liquid iron and the complex Mg-Fe-Si-Al-oxides of the Earth's lower mantle is first required(8-15). Here we present a study of the interaction between iron and silica (SiO2) in electrically and laser-heated diamond anvil cells. In a multianvil apparatus at pressures up to 140 GPa and temperatures over 3,800 K we simulate conditions down to the core-mantle boundary. At high temperature and pressures below 40 GPa, iron and silica react to form iron oxide and an iron-silicon alloy, with up to 5 wt% silicon. At pressures of 85-140 GPa, however, iron and SiO2 do not react and iron-silicon alloys dissociate into almost pure iron and a CsCl-structured (B2) FeSi compound. Our experiments suggest that a metallic silicon-rich B2 phase, produced at the core-mantle boundary (owing to reactions between iron and silicate(2,9,10,13)), could accumulate at the boundary between the mantle and core and explain the anomalously high electrical conductivity of this region(6).

Place, publisher, year, edition, pages
2003. Vol. 422, no 6927, p. 58-61
Keywords [en]
HIGH-PRESSURE; LIQUID-IRON; INNER-CORE; X-RAY; BOUNDARY; TEMPERATURES; METAL; HETEROGENEITY
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
URN: urn:nbn:se:kth:diva-7898DOI: 10.1038/nature01422ISI: 000181343100035PubMedID: 12621431Scopus ID: 2-s2.0-0037422067OAI: oai:DiVA.org:kth-7898DiVA, id: diva2:13062
Note
QC 20100624Available from: 2008-01-15 Created: 2008-01-15 Last updated: 2022-09-07Bibliographically approved
In thesis
1. Point defect interactions and structural stability of compounds
Open this publication in new window or tab >>Point defect interactions and structural stability of compounds
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Theoretical studies of point defect interactions and structural stability of compounds have been performed using density functional theory. The defect-related properties, such as activation energy of diffusion, electronic and magnetic structure of selected materials have been studied.

The major part of the present work is devoted to a very important material for semiconductor industry, GaAs. The formation energies of intrinsic point defects and the solution energies of 3d transitions in GaAs have been calculated from first principles. Based on the calculated energies, we analysed the site preference of defects in the crystal. The tendency of defects to form clusters has been investigated for the intrinsic defects as well as for impurities in GaAs. The magnetic moment of 3d impurities has been calculated as a function of the chemical environment. The possibility of increasing the Curie temperature in (Ga,Mn)As by co-doping it with Cr impurities has been examined on the basis of calculated total energy difference between the disordered local moment and the ferromagnetically ordered spin configurations. We found that, in order to reach the highest critical temperature, GaAs should be separately doped with either Cr or Mn impurities. Also, we have shown that diffusion barrier of interstitial Mn depends on the charge state of this impurity in (Ga, Mn)As. The formation of defect complexes between interstitial and substitutional Mn atoms, and their influence on the value of diffusion barrier for interstitial Mn, has been studied.

The pair interactions energies between interstitial oxygen atoms in hcp Zr, Hf and Ti have been calculated using first principles. Based on the calculated energies, the oxygen ordering structures in IVB transition metal solid solutions have been explained. A prediction of nitrogen ordering in Hf-N solid solution has been made.

The thermodynamic description of intermetallic compounds in the Zr-Sn binary system has been obtained. The conclusion has been made that Zr substitution on the Sn sites takes place in the Zr4Sn phase, which accounts for the unusual stoichiometry of this Cr3Si structure type compound.

The influence of pressure on the phase stability in the Fe-Si system has been investigated. We have found instability of the hcp Fe0.9Si0.1 random alloy with respect to the decomposition onto the Si-poor hcp Fe alloy and the B2 FeSi under high pressure. The tendency of this decomposition becomes stronger with increasing the applied pressure.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007
Keywords
first principles, ab initio, density functional theory, point defects interactions, diluted magnetic semiconductors, structural stability, zirconium alloys
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-4605 (URN)978-91-7178-842-9 (ISBN)
Public defence
2008-01-28, Sal F3, KTH, Lindstedtsvägen 26, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100624Available from: 2008-01-15 Created: 2008-01-15 Last updated: 2022-09-07Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textPubMedScopus

Search in DiVA

By author/editor
Johansson, Börje
By organisation
Materials Science and Engineering
In the same journal
Nature
Other Engineering and Technologies not elsewhere specified

Search outside of DiVA

GoogleGoogle Scholar

doi
pubmed
urn-nbn

Altmetric score

doi
pubmed
urn-nbn
Total: 90 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf