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Core-level shifts in complex metallic systems from first principle
Kyoto University, Sakyo Kyoto.
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
2006 (English)In: Physica status solidi. B, Basic research, ISSN 0370-1972, Vol. 243, no 11, 2447-2464 p.Article in journal (Refereed) Published
Abstract [en]

We show that core-level binding energy shifts (CLS) can be reliably calculated within density functional theory. The scheme includes both the initial (electron energy eigenvalue) as well as final state (relaxation due to core-hole screening) effects in the same framework. The results include CLS as a function of composition in substitutional random bulk and surface alloys. Sensitivity of the CLS to the local chemical environment in the bulk and at the surface is demonstrated. A possibility to use the CLS for structural determination is discussed. Finally, an extension of the model is made for Auger kinetic energy shift calculations.

Place, publisher, year, edition, pages
Wiley , 2006. Vol. 243, no 11, 2447-2464 p.
Keyword [en]
71.15.-m, 71.23.-k, 79.20.Fv, 79.60.Dp, 79.60.Ht, 79.60.Jv
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-37239DOI: 10.1002/pssb.200642165Local ID: 34061OAI: oai:DiVA.org:liu-37239DiVA: diva2:258088
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2013-11-14
In thesis
1. Effects of disorder in metallic systems from First-Principles calculations
Open this publication in new window or tab >>Effects of disorder in metallic systems from First-Principles calculations
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, quantum-mechanical calculations within density-functional theory on metallic systems are presented. The overarching goal has been to investigate effects of disorder. In particular, one of the properties investigated is the bindingenergy shifts for core electrons in binary alloys using different theoretical methods. These methods are compared with each other and with experimental results. One such method, the so-called Slater-Janak transition state method relies on the assumption that the single-particle eigenvalues within density-functional theory are linear functions of their respective occupation number. This assumption is investigated and it is found that while the eigenvalues to a first approximation show linear behavior, there are also nonlinearities which can influence the core-level binding energy shifts.

Another area of investigation has been iron based alloys at pressures corresponding to those in the Earth’s inner core. This has been done for the hexagonal close packed and face entered cubic structures. The effects of alloying iron with magnesium and nickel on the equation of state as well on the elastic properties have been investigated. The calculations have shown that the hexagonal close packed structure in FeNi is more isotropic than the face-centered cubic structure, and that adding Mg to Fe has a large impact on the elastic properties.

Finally, the effects of disorder due to thermal motion of the atoms have been investigated through ab-initio molecular dynamics simulations. Within the limits of this method and the setup, it is found that the face-centered cubic structure of molybdenum can be dynamically stabilized at high temperature, leading to a metastable structure, on the average. The dynamical stabilization of face-centered cubic molybdenum also rendered it possible to accurately calculate the lattice stability relative to the body-centered cubic phase. Inclusion of temperature effects for the lattice stability using ab-initio molecular dynamics simulations resolves the disagreement between ab-initio calculations and thermochemical methods.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2010. 126 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1299
Keyword
Iron, Nickel, Magnesium, Manganese, Molybdenum, Zirconium, Elastic Constants, High pressure, Earth's core, Density-functional theory, Ab-initio, First-Principles, Core-level shifts, Molecular Dynamics, Phonons, Dynamical Instability
National Category
Condensed Matter Physics Other Physics Topics
Identifiers
urn:nbn:se:liu:diva-53584 (URN)978-91-7393-445-9 (ISBN)
Public defence
2010-03-12, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2010-02-11 Created: 2010-01-25 Last updated: 2010-03-29Bibliographically approved
2. Theoretical Considerations of Local Environment Effects in Alloys
Open this publication in new window or tab >>Theoretical Considerations of Local Environment Effects in Alloys
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is devoted to a theoretical study of local environment effects in alloys. A fundamental property of a disordered system is that all chemically equivalent atoms are different due to their different chemical environments, in contrast to an ideal periodic solid where all the atoms that occupy equivalent positions in the crystal have exactly the same physical properties. The local environment effects have been largely ignored in earlier theories of disordered systems, that is the system has been treated as a whole and average properties have been derived. Moreover, inhomogeneous systems, such as surfaces and interfaces, induce local environment effects that are not necessarily present in the bulk.

The importance and presence of local environment effects are illustrated by calculating observable physical properties in various systems. In particular, by employing the complete screening picture the effects of local environments on the core-level binding energy shifts as well as Auger shifts in random alloys are in- vestigated. This so-called disorder broadening effect has recently been observed experimentally. It is shown that there are different contributions to the disorder broadening that vary with the local chemical environment. Furthermore, the influ- ence of inhomogeneous lattice distortions on the disorder broadening of the core- level photoemission spectra are considered for systems with large size-mismatch between the alloy components.

The effects of local chemical environments on physical properties in magnetic systems are illuminated. A noticeable variation in the electronic structure, local magnetic moments and exchange parameters at different sites is obtained. This reflects the sensitivity to different chemical environments and it is shown to be of qualitative importance in the vicinity of magnetic instability.

The local environment effects due to the presence of surfaces and interfaces are also considered. The effect is explicitly studied by considering the concentration profile of a thin Ag-Pd film deposited on a Ru substrate. Two computational approaches are utilized to calculate the relative composition in each layer of the thin film as a function of temperature in a theoretically consistent way. It is shown that, opposed to the situation in the bulk, where a complete solubility between Ag and Pd takes place, a non-uniform distribution of the alloy components across the film is observed.

In another study it is investigated whether the presence of TiN interfaces changes the dynamical and thermodynamic stability of B1 SiN. Phonon calcula- tions show that TiN interfaces have a stabilization effect on the lattice dynamics. On the other hand, calculations of the Si vacancy formation energy show that the structures are unstable with respect to composition variations.

 

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2010. 86 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1353
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-63443 (URN)978-91-7393-285-1 (ISBN)
Public defence
2010-12-17, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2010-12-27 Created: 2010-12-19 Last updated: 2010-12-27Bibliographically approved
3. Spectroscopic and elastic properties in metallic systems from first-principles methods
Open this publication in new window or tab >>Spectroscopic and elastic properties in metallic systems from first-principles methods
2007 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, ab initio calculations on metallic systems are presented. The overall aim is to probe properties that are often considered to be difficult to obtain within the framework of density-functional theory. The aim has also been to chose problems and systems that are of a wider interest and not only a testbed for calculations.

One of the properties investigated is the binding-energy shifts for core electrons in binary alloys of face-centered cubic structure using different theoretical methods. These methods are compared with each other and with experimental results. One of the methods, the so-called Slater-Jank transition state method has been investigated in more detail. This method relies on the assumption that the single-particle eigenvalues within density-functional theory are linear functions of their respective occupation number. This assumption is investigated , and it is found that while the eigenvalues to a first approximation show linear behaviour, the Slater-Jank transition state method can be improved by a first-order correction to the non-linearities.

Another area of investigation have been FeNi systems at high pressure. Calculations of elastic constants in this alloy at pressures corresponding to the Earth's core have been done for the hexagonal close packed and face centered cubic structures. These calculations show that, contrary to many other systems, the hexagonal close packed structure in FeNi is more isotropic than the face centered cubic structure.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2007. 60 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1314
Series
LIU-TEK-LIC, 23
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-37986 (URN)40827 (Local ID)978-91-85831-784 (ISBN)40827 (Archive number)40827 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2013-11-14

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Asker, ChristianMarten, TobiasAbrikosov, Igor

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