Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • 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
Role of defects in Ti(O,C)
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.ORCID iD: 0000-0002-9920-5393
(English)Manuscript (preprint) (Other academic)
National Category
Condensed Matter Physics
Research subject
Materials Science and Engineering; Physics
Identifiers
URN: urn:nbn:se:kth:diva-223666OAI: oai:DiVA.org:kth-223666DiVA, id: diva2:1186240
Funder
VINNOVA, 2012-02892
Note

QC 20180228

Available from: 2018-02-27 Created: 2018-02-27 Last updated: 2018-02-28Bibliographically approved
In thesis
1. Finite temperature properties of elements and alloy phases from first principles
Open this publication in new window or tab >>Finite temperature properties of elements and alloy phases from first principles
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

First principles calculations are usually concerned with properties calculated at temperature 0 K. However, the industrially important materials are functioning at finite temperatures. To fill such a gap a first-principles based modeling of free energy has been developed in this thesis and finite temperature properties of different phases of Fe and Mn have been calculated and contrasted with available experimental data.

In particular, using partitioning of the Helmholtz free energy, thermophysical properties of paramagnetic Fe have been reported. The heat capacity, lattice constant, thermal expansion and elastic moduli of γ- and δ-Fe show a good agreement with available experimental data. In the case of α-Fe, we observe a good agreement for elastic moduli and thermal expansion with experiments but the heat capacity is not well-reproduced in the calculations because of the large contribution of magnetic short-range which our models are not capable of capturing.

α- and β-Mn theoretically pose a challenge for direct simulations of thermodynamic properties because of the complexity of magnetic and crystal structure. The partitioning of free energy has been used and thermodynamics of these phases have been derived. The obtained results show a good agreement with experimental data suggesting that, despite the complexities of these phases, a rather simple approach can well describe their finite temperature properties. High temperature phases of Mn, γ and δ, are also theoretically challenging problems. Employing a similar approach to Fe, thermophysical properties of these high symmetry phases of Mn have been reported which also show good agreement with available experimental data.

The point defect and metal-self diffusion in titanium carbide (TiC), a refractory material, have been investigated in the present work. The common picture of metal-vacancy exchange mechanism for metal self-diffusion was shown to be unable to explain the experimentally observed values of activation energy. Several new clusters of point defects such as vacancies and interstitials have been found and reported which are energetically lower that a single metal vacancy. In a subsequent study, we showed that some of these clusters can be considered as mediators of metal self-diffusion in TiC.

Evaluation of structural properties of Ti(O,C), a solid solution of TiC and β-TiO, from supercell approach is an extremely difficult task. For a dilute concentration of O, we show the complexity of describing an impurity of O in TiC using supercell approach. A single-site method such as the exact muffin-tin orbital method in the coherent potential approximation (EMTO-CPA) is a good alternative to supercell modeling of Ti(O,C). However, a study of Ti(O,C) using EMTO-CPA requires a further development of the technique regarding the partitioning of space. The shape module of EMTO has been modified for this purpose. With the help of the modified module, Ti(O,C) have been studied using EMTO-CPA. The results for the divacancy concentration and corresponding lattice parameter variations show good agreement with experimental data.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. p. 78
National Category
Condensed Matter Physics
Research subject
Materials Science and Engineering; Physics
Identifiers
urn:nbn:se:kth:diva-223668 (URN)978-91-7729-687-4 (ISBN)
Public defence
2018-03-26, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
VINNOVA
Note

QC 20180228

Available from: 2018-02-28 Created: 2018-02-27 Last updated: 2018-03-08Bibliographically approved

Open Access in DiVA

No full text in DiVA

Authority records BETA

Ehteshami, HosseinRuban, Andrei V.Korzhavyi, Pavel A.

Search in DiVA

By author/editor
Ehteshami, HosseinRuban, Andrei V.Korzhavyi, Pavel A.
By organisation
Materials Science and EngineeringMaterials Science and Engineering
Condensed Matter Physics

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 16 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • 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