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Numerical investigation of the validity of the Slater-Janak transition-state model in metallic systems
Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
Condensed Matter Theory Group, Department of Physics, Uppsala University.
Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
2005 (engelsk)Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 72, nr 13Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
2005. Vol. 72, nr 13
HSV kategori
Identifikatorer
URN: urn:nbn:se:liu:diva-12559DOI: 10.1103/PhysRevB.72.134203OAI: oai:DiVA.org:liu-12559DiVA, id: diva2:1702
Merknad

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/

Tilgjengelig fra: 2008-09-15 Laget: 2008-09-15 Sist oppdatert: 2017-12-14
Inngår i avhandling
1. Effects of disorder in metallic systems from First-Principles calculations
Åpne denne publikasjonen i ny fane eller vindu >>Effects of disorder in metallic systems from First-Principles calculations
2010 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Linköping: Linköping University Electronic Press, 2010. s. 126
Serie
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1299
Emneord
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
HSV kategori
Identifikatorer
urn:nbn:se:liu:diva-53584 (URN)978-91-7393-445-9 (ISBN)
Disputas
2010-03-12, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2010-02-11 Laget: 2010-01-25 Sist oppdatert: 2010-03-29bibliografisk kontrollert
2. Spectroscopic and elastic properties in metallic systems from first-principles methods
Åpne denne publikasjonen i ny fane eller vindu >>Spectroscopic and elastic properties in metallic systems from first-principles methods
2007 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Linköping: Linköpings universitet, 2007. s. 60
Serie
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1314
Serie
LIU-TEK-LIC ; 23
HSV kategori
Identifikatorer
urn:nbn:se:liu:diva-37986 (URN)40827 (Lokal ID)978-91-85831-784 (ISBN)40827 (Arkivnummer)40827 (OAI)
Tilgjengelig fra: 2009-10-10 Laget: 2009-10-10 Sist oppdatert: 2013-11-14

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