| 1. |
- Olovsson, Weine, et al.
(författare)
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Core-level shifts in complex metallic systems from first principle
- 2006
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Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 243:11, s. 2447-2464
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
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| 4. |
- Asker, Christian, 1979-
(författare)
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Effects of disorder in metallic systems from First-Principles calculations
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 5. |
- Asker, Christian, 1979-, et al.
(författare)
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Electronic and atomic structure of Mo from high-temperature molecular dynamics simulations
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Annan publikation (populärvet., debatt m.m.)abstract
- By means of ab initio molecular dynamics (AIMD) simulations we carry out a detailed stdly of the electronic and atomic structure of Mo upon the thermal stabilization of its dynamically unstable face-centered cubic (fcc) phase, Wc calculate how the atomic positions, radial distribution function, and the ei
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| 6. |
- Asker, Christian, 1979-, et al.
(författare)
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Equation of state and elastic properties of face-centered cubic FeMg alloy at ultrahigh pressures from first-principles
- 2010
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Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 0012-821X .- 1385-013X. ; 293:1-2, s. 130-134
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Tidskriftsartikel (refereegranskat)abstract
- We have ca1culated the equation of state and elastic properties of face-centered cubic Fe and Fe-rich FeMg alloy at ultrahigh pressures from first principles using the Exact Muffin-Tin Orbitals method. The results show that adding Mg into Fe influences strongly the equation of state, and cause a large degree of softening of the elastic constants, even at concentrations as small as 1-2 at. %. Moreover, the e1astic anisotropy increases, and the effect is higher at higher pressures.
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| 7. |
- Asker, Christian, 1979-
(författare)
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Spectroscopic and elastic properties in metallic systems from first-principles methods
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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