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Spectroscopic and elastic properties in metallic systems from first-principles methods
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
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: urn:nbn:se:liu:diva-37986Local ID: 40827ISBN: 978-91-85831-784 OAI: oai:DiVA.org:liu-37986DiVA: diva2:258835
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2013-11-14
List of papers
1. Core-level shifts in fcc random alloys: A first-principles approach
Open this publication in new window or tab >>Core-level shifts in fcc random alloys: A first-principles approach
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2005 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 72, no 6, 064203- p.Article in journal (Refereed) Published
Abstract [en]

First-principles theoretical calculations of the core-level binding-energy shift (CLS) for eight binary face-centered-cubic (fcc) disordered alloys, CuPd, AgPd, CuNi, NiPd, CuAu, PdAu, CuPt, and NiPt, are carried out within density-functional theory (DFT) using the coherent potential approximation. The shifts of the Cu and Ni 2p3∕2, Ag and Pd 3d5∕2, and Pt and Au 4f7∕2 core levels are calculated according to the complete screening picture, which includes both initial-state (core-electron energy eigenvalue) and final-state (core-hole screening) effects in the same scheme. The results are compared with available experimental data, and the agreement is shown to be good. The CLSs are analyzed in terms of initial- and final-state effects. We also compare the complete screening picture with the CLS obtained by the transition-state method, and find very good agreement between these two alternative approaches for the calculations within the DFT. In addition the sensitivity of the CLS to relativistic and magnetic effects is studied.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-12565 (URN)10.1103/PhysRevB.72.064203 (DOI)
Note

Original publication: W. Olovsson, C. Göransson, L. V. Pourovskii, B. Johansson and I. A. Abrikosov, Core-level shifts in fcc random alloys: A first-principles approach, 2005, Physical Review B, (72), 064203. Copyright: The America Physical Society, http://prb.aps.org/

Available from: 2008-09-15 Created: 2008-09-15 Last updated: 2017-12-14
2. Numerical investigation of the validity of the Slater-Janak transition-state model in metallic systems
Open this publication in new window or tab >>Numerical investigation of the validity of the Slater-Janak transition-state model in metallic systems
2005 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 72, no 13Article in journal (Refereed) Published
Abstract [en]

According to the so-called Janak’s theorem, the eigenstates of the Kohn-Sham Hamiltonian are given by the derivative of the total energy with respect to the occupation numbers of the corresponding one-electron states. The linear dependence of the Kohn-Sham eigenvalues on the occupation numbers is often assumed in order to use the Janak’s theorem in applications, for instance, in calculations of the core-level shifts in materials by means of the Slater-Janak transition state model. In this work first-principles density-functional theory calculations using noninteger occupation numbers for different core states in 24 different random alloy systems were carried out in order to verify the assumptions of linearity. It is found that, to a first approximation, the Kohn-Sham eigenvalues show a linear behavior as a function of the occupation numbers. However, it is also found that deviations from linearity have observable effects on the core-level shifts for some systems. A way to reduce the error with minimal increase of computational efforts is suggested.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-12559 (URN)10.1103/PhysRevB.72.134203 (DOI)
Note

Original publication: C. Göransson, W. Olovsson and I. A. Abrikosov, Numerical investigation of the validity of the Slater-Janak transition-state model in metallic systems, 2005, Physical Review B, (72), 134203. Copyright: The America Physical Society, http://prb.aps.org/

Available from: 2008-09-15 Created: 2008-09-15 Last updated: 2017-12-14
3. Core-level shifts in complex metallic systems from first principle
Open this publication in new window or tab >>Core-level shifts in complex metallic systems from first principle
2006 (English)In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, 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
Keyword
71.15.-m, 71.23.-k, 79.20.Fv, 79.60.Dp, 79.60.Ht, 79.60.Jv
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-37239 (URN)10.1002/pssb.200642165 (DOI)34061 (Local ID)34061 (Archive number)34061 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13

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